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TITLEEvaluating the accuracy and precision of sonographic fetal weight estimation models in extremely early-onset fetal growth restrictionAUTHORSLynne K WARRANDER MBChB MRes, Manchester, UK1, 2Emma INGRAM MBChB PhD MRCOG, Manchester, UK1, 2Alexander EP HEAZELL MBChB(Hons) PhD MRCOG, Manchester, UK1, 2Edward D JOHNSTONE MBChB PhD MRCOG, Manchester, UK1, 21 Maternal & Fetal Health Research Centre, Division of Developmental Biology, Medicine & Health, School of Medical Sciences, Faculty of Biology, Medicine & Health, The University of Manchester, Manchester, UK2 St Mary’s Hospital, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, UKCorresponding authorLynne WarranderMaternal and Fetal Health Research Centre, 5th floor (research) St Mary’s Hospital, Oxford Road, Manchester, M13 9WLTel 0044 161 7016960Email: lynne.warrander@manchester.ac.ukCONFLICT OF INTERESTThe authors declare there is no conflict of interest.FUNDINGThis study was funded by Tommy’s the baby charity. The funding source had no involvement in the study design, manuscript preparation or decision to publish.ABSTRACTIntroductionBirthweight is a critical predictor of survival in extremely early-onset fetal growth restriction (fetal growth restriction diagnosed pre-28 weeks’ gestation, with abnormal umbilical/uterine artery Doppler waveforms), therefore accurate fetal weight estimation is a crucial component of antenatal management. Currently available sonographic fetal weight estimation models were predominantly developed in populations of mixed gestational age and varying fetal weights, but not specifically tested within the context of extremely early-onset fetal growth restriction. This study aimed to determine the accuracy and precision of fetal weight estimation in this population and investigate if model performance is affected by other factors.Materials & MethodsCases where a growth scan was performed within 48 hours of delivery (n=65) were identified from a cohort of extremely early-onset fetal growth restricted pregnancies at a single tertiary maternity centre (n=159). Fetal biometry measurements were used to calculate estimated fetal weight using 21 previously published models. Systematic and random errors were calculated for each model and used to identify the best performing model, which in turn was used to explore the relationship between error and gestation, estimated fetal weight, fetal presentation, fetal asymmetry and amniotic fluid volume.ResultsBoth systematic (median 8.2%; range -44.1% – 49.5%) and random error (median 11.6%; range 9.7% – 23.8%) varied widely across models. The best performing model was Hadlock HC-AC-FL, regardless of gestational age, fetal size, fetal presentation or asymmetry, with an overall systematic error of 1.5% and random error of 9.7%. Despite this, it only calculated the estimated fetal weight within 10% of birthweight in 64.6% of cases. There was a weak negative relationship between mean percentage error with Hadlock HC-AC-FL and amniotic fluid volume, suggesting fetal weight is overestimated at lower liquor volumes and underestimated at higher liquor volumes (P=0.002, adjusted R2=0.08).ConclusionsHadlock HC-AC-FL is the most accurate model currently available to estimate fetal weight in extremely early-onset fetal growth restriction independent of gestation or fetal size, asymmetry or presentation. However, for 35.4% of cases in this study, estimated fetal weight calculated using this model deviates by more than 10% from birthweight, highlighting a need for an improved model.KEY WORDSantenatal assessment; antenatal ultrasound; fetal growth; fetal growth restriction; prematurity; sonographic fetal weight models; survival predictionABBREVIATIONSACAbdominal circumferenceAFIAmniotic fluid indexBPDBiparietal diameterEDFEnd diastolic flowEFWEstimated fetal weighteFGRExtremely early-onset fetal growth restrictionFGRFetal growth restrictionFLFemur lengthHCHead circumferenceSGASmall for gestational ageWord countAbstract: 349 words. Main text: 3000 wordsKEY MESSAGEHadlock HC-AC-FL is the most accurate sonographic weight estimation model in extremely early-onset fetal growth restriction, regardless of gestation, fetal weight or fetal presentation.INTRODUCTION Fetal growth restriction (FGR) can be classified by the gestation at diagnosis, with 32 weeks’ typically differentiating early from late-onset diseaseADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.15884","ISBN":"1469-0705 (Electronic)\r0960-7692 (Linking)","PMID":"26909664","abstract":"OBJECTIVE: To determine, by expert consensus, a definition for early and late fetal growth restriction (FGR) through a Delphi procedure. METHOD: A Delphi survey was conducted among an international panel of experts on FGR. Panel members were provided with 18 literature-based parameters for defining FGR and were asked to rate the importance of these parameters for the diagnosis of both early and late FGR on a 5-point Likert scale. Parameters were described as solitary parameters (parameters that are sufficient to diagnose FGR, even if all other parameters are normal) and contributory parameters (parameters that require other abnormal parameter(s) to be present for the diagnosis of FGR). Consensus was sought to determine the cut-off values for accepted parameters. RESULTS: A total of 106 experts were approached, of whom 56 agreed to participate and entered the first round, and 45 (80%) completed all four rounds. For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon. For late FGR (>/= 32 weeks), two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined. CONCLUSION: Consensus-based definitions for early and late FGR, as well as cut-off values for parameters involved, were agreed upon by a panel of experts. Copyright (c) 2016 ISUOG. Published by John Wiley & Sons Ltd.","author":[{"dropping-particle":"","family":"Gordijn","given":"S J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beune","given":"I M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Thilaganathan","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Papageorghiou","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Baschat","given":"A A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Baker","given":"P N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Silver","given":"R M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wynia","given":"K","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ganzevoort","given":"W","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound Obstet Gynecol","id":"ITEM-1","issue":"3","issued":{"date-parts":[["2016"]]},"note":"Gordijn, S J\nBeune, I M\nThilaganathan, B\nPapageorghiou, A\nBaschat, A A\nBaker, P N\nSilver, R M\nWynia, K\nGanzevoort, W\neng\nEngland\n2016/02/26 06:00\nUltrasound Obstet Gynecol. 2016 Sep;48(3):333-9. doi: 10.1002/uog.15884.","page":"333-339","title":"Consensus definition of fetal growth restriction: a Delphi procedure","type":"article-journal","volume":"48"},"uris":[""]}],"mendeley":{"formattedCitation":"(1)","plainTextFormattedCitation":"(1)","previouslyFormattedCitation":"(1)"},"properties":{"noteIndex":0},"schema":""}(1). Within early-onset FGR, there is an extreme cohort (eFGR), typically diagnosed pre-28 weeks’ gestation which is associated with severe placental dysfunction, and particularly features of maternal vascular malperfusionADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1159/000359969","ISBN":"1015-3837","PMID":"24577279","abstract":"Several histopathological features are found more frequently in placentas from pregnancies complicated by fetal growth restriction (FGR), including villous infarction, maternal vascular changes and villous morphological alterations, although around one quarter of placentas associated with FGR lack any morphological abnormality on routine examination. Since similar changes may also affect clinically uncomplicated pregnancies, the positive predictive value of such findings for pathological FGR in an unselected case remains low. However, the pattern of placental pathologies varies with clinical subgroup. The combination of placental bed and parenchymal lesions in FGR with abnormal uterine artery Doppler velocimetry is essentially identical to preterm pre-eclampsia (PET), and there is an association between FGR with abnormal umbilical artery Doppler findings and lesions of fetal stem arteries and terminal villous hypovascularity. Conversely, placentas from pregnancies complicated by PET or FGR presenting at or near term have a significantly lower frequency of histological abnormalities compared to early-onset disease and absence of a distinctive biochemical profile. The histological placental findings in FGR are therefore varied, from morphologically unremarkable through to severe uteroplacental vasculopathy, with no single pathological feature associated with high sensitivity or specificity. Severe early-onset FGR, overlapping with severe early-onset PET, is mainly associated with features of impaired maternal uteroplacental perfusion secondary to defective extravillous trophoblast invasion, and its consequences. Late-onset FGR probably represents a more heterogeneous group with less characteristic histological changes. Future research using histopathological assessment of aggregated data from multiple studies into larger datasets with centralised pathology review will allow delineation of distinctive clinicopathological associations and further understanding of pathophysiology. (C) 2014 S. Karger AG, Basel","author":[{"dropping-particle":"","family":"Mifsud","given":"William","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sebire","given":"Neil J","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Fetal Diagn Ther","id":"ITEM-1","issue":"2","issued":{"date-parts":[["2014"]]},"note":"From Duplicate 2 (Placental pathology in early-onset and late-onset fetal growth restriction - Mifsud, W; Sebire, N J)\n\nMifsud, William\nSebire, Neil J\neng\nReview\nSwitzerland\n2014/03/01 06:00\nFetal Diagn Ther. 2014;36(2):117-28. doi: 10.1159/000359969. Epub 2014 Feb 21.","page":"117-128","title":"Placental pathology in early-onset and late-onset fetal growth restriction","type":"article-journal","volume":"36"},"uris":[""]}],"mendeley":{"formattedCitation":"(2)","plainTextFormattedCitation":"(2)","previouslyFormattedCitation":"(2)"},"properties":{"noteIndex":0},"schema":""}(2). Although rare, mortality rates are disproportionately high in this cohort; a recent study investigating sildenafil citrate as a therapy to improve fetal growth in utero in eFGR had a 32% stillbirth rateADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/S2352-4642(17)30173-6","ISSN":"23524642","abstract":"<h2>Summary</h2><h3>Background</h3><p>Severe early-onset fetal growth restriction can lead to a range of adverse outcomes including fetal or neonatal death, neurodisability, and lifelong risks to the health of the affected child. Sildenafil, a phosphodiesterase type 5 inhibitor, potentiates the actions of nitric oxide, which leads to vasodilatation of the uterine vessels and might improve fetal growth in utero.</p><h3>Methods</h3><p>We did this superiority, placebo-controlled randomised trial in 19 fetal medicine units in the UK. We used random computer allocation (1:1) to assign women with singleton pregnancies between 22 weeks and 0 days' gestation and 29 weeks and 6 days' gestation and severe early-onset fetal growth restriction to receive either sildenafil 25 mg three times daily or placebo until 32 weeks and 0 days' gestation or delivery. We stratified women by site and by their gestational age at randomisation (before week 26 and 0 days or at week 26 and 0 days or later). We defined fetal growth restriction as a combination of estimated fetal weight or abdominal circumference below tenth percentile and absent or reversed end-diastolic blood flow in the umbilical artery on Doppler velocimetry. The primary outcome was the time from randomisation to delivery, measured in days. This study is registered with BioMed Central, number ISRCTN 39133303.</p><h3>Findings</h3><p>Between Nov 21, 2014, and July 6, 2016, we recruited 135 women and randomly assigned 70 women to sildenafil and 65 women to placebo. We found no difference in the median randomisation to delivery interval between women assigned to sildenafil (17 days [IQR 7–24]) and women assigned to placebo (18 days [8–28]; p=0·23). Livebirths (relative risk [RR] 1·06, 95% CI 0·84 to 1·33; p=0·62), fetal deaths (0·89, 0·54 to 1·45; p=0·64), neonatal deaths (1·33, 0·54 to 3·28; p=0·53), and birthweight (?14 g,–100 to 126; p=0·81) did not differ between groups. No differences were found for any other secondary outcomes. Eight serious adverse events were reported during the course of the study (six in the placebo group and two in the sildenafil group); none of these were attributed to sildenafil.</p><h3>Interpretation</h3><p>Sildenafil did not prolong pregnancy or improve pregnancy outcomes in severe early-onset fetal growth restriction and therefore it should not be prescribed for this indication outside of research studies with explicit participants' consent.</p><h3>Funding</h3><p>National Institute for…","author":[{"dropping-particle":"","family":"Sharp","given":"Andrew","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Cornforth","given":"Christine","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Jackson","given":"Richard","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrold","given":"Jane","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Turner","given":"Mark A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kenny","given":"Louise C","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Baker","given":"Philip N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Johnstone","given":"Edward 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Lancet Child & Adolescent Health","id":"ITEM-1","issue":"2","issued":{"date-parts":[["2017","12","1"]]},"page":"93-102","publisher":"Elsevier","title":"Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial","type":"article-journal","volume":"2"},"uris":[""]}],"mendeley":{"formattedCitation":"(3)","plainTextFormattedCitation":"(3)","previouslyFormattedCitation":"(3)"},"properties":{"noteIndex":0},"schema":""}(3). The challenge for obstetricians is to balance timing of delivery to minimise the risk of stillbirth from prolonging the pregnancy, against the risks of neonatal mortality and morbidity associated with delivery at such extremes of weight and gestation. Birthweight is one of the most important predictors of survival in preterm births, (survival to discharge following live birth in England between 2008-2014 increasing from 34.8% when birthweight is less than 500g, to 76.8% for a birthweight of 500-1000gADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1136/archdischild-2017-312748","ISSN":"1468-2052","PMID":"28883097","abstract":"OBJECTIVE To analyse survival trends and regional variation for very preterm infants admitted to neonatal care. SETTING All neonatal units in England. PATIENTS Infants born at 22+0-31+6 weeks+daysgestational age (GA) over 2008-2014 and admitted to neonatal care; published data for admitted infants 22+0-25+6 weeks+days GA in 1995 and 2006, and for live births at 22+0-31+6 weeks+days GA in 2013. METHODS We obtained data from the National Neonatal Research Database. We used logistic regression to model survival probability with birth weight, GA, sex, antenatal steroid exposure and multiple birth included in the risk adjustment model and calculated annualpercentage change (APC) for trends using joinpoint regression. We evaluated survival over a 20-year period for infants <26 weeks' GA using additional published data from the EPICure studies. RESULTS We identified 50?112 eligible infants. There was an increase in survival over 2008-2014 (2008: 88.0%; 2014: 91.3%; adjusted APC 0.46% (95% CI 0.30 to 0.62)?p<0.001). The greatest improvement was at 22+0-23+6 weeks (APC 6.03% (95% CI 2.47 to 3.53) p=0.002). Improvement largely occurred in London and South of England (APC: London 1.26% (95% CI 0.60 to 1.96); South of England 1.09% (95% CI 0.36 to 1.82); Midlands and East of England 0.15% (95% CI -0.56 to 0.86); and North of England 0.26% (95% CI -0.54 to 1.07)). Survival at the earliest gestations improved at a similar rate over 1995-2014 (22+0-25+6 weeks, APC 2.73% (95% CI 2.35 to 3.12),?p value for change=0.25). CONCLUSIONS Continued national improvement in the survival of very preterm admissions masks important regional variation. Timely assessment of preterm survival is feasible using electronic records.","author":[{"dropping-particle":"","family":"Santhakumaran","given":"Shalini","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Statnikov","given":"Yevgeniy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gray","given":"Daniel","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Battersby","given":"Cheryl","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ashby","given":"Deborah","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Modi","given":"Neena","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Medicines for Neonates Investigator Group","given":"","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Archives of disease in childhood. Fetal and neonatal edition","id":"ITEM-1","issue":"3","issued":{"date-parts":[["2018","5","1"]]},"page":"F208-F215","publisher":"BMJ Publishing Group","title":"Survival of very preterm infants admitted to neonatal care in England 2008-2014: time trends and regional variation.","type":"article-journal","volume":"103"},"uris":[""]}],"mendeley":{"formattedCitation":"(4)","plainTextFormattedCitation":"(4)"},"properties":{"noteIndex":0},"schema":""}(4)), though it should be noted that contemporary data on gestation-specific survival in eFGR infants is limited. It follows therefore that accurate determination of estimated fetal weight (EFW) is a crucial component of antenatal management and plays an important role in the delivery decision when preterm delivery is indicated. Currently in the UK, Hadlock HC-AC-FL is the recommended sonographic weight estimation modelADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.1971","ISSN":"09607692","author":[{"dropping-particle":"","family":"Gardosi","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2005"]]},"title":"Fetal growth: Towards an international standard","type":"article"},"uris":[""]}],"mendeley":{"formattedCitation":"(5)","plainTextFormattedCitation":"(5)","previouslyFormattedCitation":"(6)"},"properties":{"noteIndex":0},"schema":""}(5). However, this was developed using a cohort of 276 mixed gestational age fetuses from a Caucasian background, and included both growth-restricted, appropriately grown and macrosomic fetusesADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6), and therefore may not be the most accurate model within the context of eFGR. Other models have been developed in appropriately grown and small for gestational age (SGA) populations and preterm populationsADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"ISSN":"0278-4297","PMID":"8887237","abstract":"Most estimated fetal weight formulas have been derived and tested with larger fetuses, yet accuracy in predicting birth weight is more critical at the limit of viability. Complete data from 142 pregnancies in which delivery took place within 7 days of an ultrasonographic examination were used to create an appropriate formula for fetuses less than 1000 g and compare it with 10 currently available formulas. Our formula (In [BW] = 0.66 x 1n [HC] + 1.04 x 1n [AC] + 0.985 x 1n [FL]) was significantly more accurate than all other formulas and also performed better on a prospective cohort of 27 fetuses with estimated fetal weight less than 1000 g. Of the existing formulas, the Hadlock formula (using head circumference, abdominal circumference, femur length) was the most accurate, being significantly more accurate than all but the Woo formula with all but the Woo formula.","author":[{"dropping-particle":"","family":"Scott","given":"F","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beeby","given":"P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Abbott","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Edelman","given":"D","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Boogert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine","id":"ITEM-1","issue":"10","issued":{"date-parts":[["1996","10"]]},"page":"669-72","title":"New formula for estimating fetal weight below 1000 g: comparison with existing formulas.","type":"article-journal","volume":"15"},"uris":[""]},{"id":"ITEM-2","itemData":{"DOI":"10.1002/uog.1741","ISSN":"09607692","author":[{"dropping-particle":"","family":"Schild","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fell","given":"K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fimmers","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gembruch","given":"U.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hansmann","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-2","issue":"7","issued":{"date-parts":[["2004","12","1"]]},"page":"775-780","publisher":"John Wiley & Sons, Ltd","title":"A new formula for calculating weight in the fetus of ≤ 1600 g","type":"article-journal","volume":"24"},"uris":[""]},{"id":"ITEM-3","itemData":{"DOI":"10.1055/s-2007-963645","ISSN":"0172-4614","PMID":"19137495","abstract":"PURPOSE Birth weight is an important predictive parameter for neonatal morbidity and mortality in the small fetus. Accurate estimation of fetal weight is therefore a valuable tool for determining the further obstetric management. The majority of studies presenting new formulas have included relatively small samples with a narrow range of birth weights, mostly term fetuses. In a previous study, we evaluated several weight formulas over the whole range of birth weights and in defined subgroups. We were able to show that some regression formulas appeared to be favorable within these subgroups. Notably, the highest levels of inaccuracy were found in the group of infants with a birth weight of less than 2500 g. This led us to hypothesize that a formula based on the lower birth weight group might increase the accuracy of weight estimation. The aim of the present study was therefore to develop a new specific formula for estimating weight in fetuses less than or equal to 2500 g and to compare the new regression formula with commonly used weight equations. MATERIALS AND METHODS This study included 260 pregnancies. The inclusion criteria were a singleton pregnancy; birth weight equal to or less than 2500 g; an ultrasound examination with complete biometric parameters within 7 days prior to delivery; and an absence of structural or chromosomal malformations. The data for the first 130 newborns were used to develop a new formula. The remaining 130 infants were used to evaluate the new regression formula and to compare it to commonly used weight equations. Stepwise regression analysis was carried out with the birth weight as the dependent variable and biometric parameters as independent parameters to obtain the best-fit formula. RESULTS The mean absolute percentage error for the new formula was 7.71 %. Compared to the other formulas, it generated the highest intraclass correlation coefficient. By the limits of agreement, the new formula demonstrated only a slight tendency towards underestimating fetal weight, and it provided the smallest range of all weight equations. CONCLUSION With proper application, our new formula can improve the accuracy of fetal weight estimation.","author":[{"dropping-particle":"","family":"Siemer","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hilbert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hart","given":"N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Meurer","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Goecke","given":"T","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Schild","given":"R","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultraschall in der Medizin - European Journal of Ultrasound","id":"ITEM-3","issue":"01","issued":{"date-parts":[["2009","1","9"]]},"page":"47-51","title":"A New Sonographic Weight Formula for Fetuses?≤?2500 g","type":"article-journal","volume":"30"},"uris":[""]},{"id":"ITEM-4","itemData":{"DOI":"10.1016/0002-9378(83)91195-X","ISSN":"0002-9378","abstract":"Based on ultrasonographic mensuration, a number of equations have previously been devised for the purpose of estimating fetal weights. The objective of this study was to develop a mathematical equation that is simple, accurate, and easy to use when applied to preterm or low-birth weight fetuses (<2,500 gm). Real-time ultrasound measurements of fetal biparietal diameters (BPDs) and abdominal circumferences (ACs) were obtained in 62 pregnant women within one week of premature delivery. Mean gestational age and mean birth weight ± SD for this study group of neonates were 28.5 ± 3.5 weeks and 1,135 ± 343 gm, respectively. With the aid of computer analysis, a simple regression equation was derived: EFW = (BPD x AC x 9.337) ?299. When predicted estimated fetal weight (EFW) was compared with actual birth weight (ABW), multiple regression analysis demonstrated a correlation coefficient (R) of 0.957. Preliminary results on 19 oatients of a prospective study showed an absolute mean difference between the computed EFWs and the ABWs to be within 7.0% of ABW (70 gm/kg of ABW). The standard deviation of the difference was 9.3% of ABW (93 gm/kg of ABW). Based on these data, this simple equation appears to be clinically reliable and easy to use when estimating weights of preterm or low-birth weight fetuses of less than 2,500 gm.","author":[{"dropping-particle":"","family":"Thurnau","given":"Gary R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Tamura","given":"Ralph K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sabbagha","given":"Rudy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Depp","given":"O.Richard","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Dyer","given":"Alan","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Larkin","given":"Ron","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Lee","given":"Timothy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Laughlin","given":"Colby","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-4","issue":"5","issued":{"date-parts":[["1983","3","1"]]},"page":"557-561","publisher":"Mosby","title":"A simple estimated fetal weight equation based on real-time ultrasound measurements of fetuses less than thirty-four weeks' gestation","type":"article-journal","volume":"145"},"uris":[""]}],"mendeley":{"formattedCitation":"(7–10)","plainTextFormattedCitation":"(7–10)","previouslyFormattedCitation":"(8–11)"},"properties":{"noteIndex":0},"schema":""}(7–10) but have never been directly compared to one another in an eFGR cohort. Previous research has suggested that the choice of model in an SGA population may depend on other factors, such as gestation, symmetrical/asymmetrical growth or Doppler abnormalitiesADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.7863/ultra.15.02058","ISSN":"02784297","author":[{"dropping-particle":"","family":"Melamed","given":"Nir","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ryan","given":"Greg","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Windrim","given":"Rory","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Toi","given":"Ants","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kingdom","given":"John","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of Ultrasound in Medicine","id":"ITEM-1","issue":"1","issued":{"date-parts":[["2016","1","1"]]},"page":"71-82","publisher":"John Wiley & Sons, Ltd","title":"Choice of Formula and Accuracy of Fetal Weight Estimation in Small-for-Gestational-Age Fetuses","type":"article-journal","volume":"35"},"uris":[""]}],"mendeley":{"formattedCitation":"(11)","plainTextFormattedCitation":"(11)","previouslyFormattedCitation":"(12)"},"properties":{"noteIndex":0},"schema":""}(11). This study firstly aimed to determine the error in EFW in a cohort of eFGR pregnancies using the recommended Hadlock models, and subsequently EFW error using different models identified in the literature, including some specifically developed in a population of FGR/SGA pregnancies. Secondly, it aimed to determine if accuracy was influenced by factors such as gestational age, EFW, fetal presentation, fetal asymmetry (disproportionately reduced growth of abdominal circumference compared to head circumference as a consequence of maintaining essential organ growth) and amniotic fluid volume. MATERIALS AND METHODSThis was a retrospective cohort study of patients with a diagnosis of eFGR, managed through translational research clinics at a high-risk tertiary referral unit between June 2009-September 2018. Cases were retrospectively identified, and relevant ultrasound measurements collected from an electronic database. Only those pregnancies where the fetus was alive and a growth scan was performed within 48 hours of delivery were included. Exclusion criteria encompassed multiple pregnancy, known fetal abnormality, missing fetal ultrasound biometry data and incomplete pregnancy outcome data. Diagnosis of eFGR was based on the Delphi consensus definition (EFW/AC below the 3rd centile for gestation, or EFW/AC between 3rd-10th centile, with a pulsatility index above the 95th centile for gestation in the umbilical or uterine arteriesADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.15884","ISBN":"1469-0705 (Electronic)\r0960-7692 (Linking)","PMID":"26909664","abstract":"OBJECTIVE: To determine, by expert consensus, a definition for early and late fetal growth restriction (FGR) through a Delphi procedure. METHOD: A Delphi survey was conducted among an international panel of experts on FGR. Panel members were provided with 18 literature-based parameters for defining FGR and were asked to rate the importance of these parameters for the diagnosis of both early and late FGR on a 5-point Likert scale. Parameters were described as solitary parameters (parameters that are sufficient to diagnose FGR, even if all other parameters are normal) and contributory parameters (parameters that require other abnormal parameter(s) to be present for the diagnosis of FGR). Consensus was sought to determine the cut-off values for accepted parameters. RESULTS: A total of 106 experts were approached, of whom 56 agreed to participate and entered the first round, and 45 (80%) completed all four rounds. For early FGR (< 32 weeks), three solitary parameters (abdominal circumference (AC) < 3(rd) centile, estimated fetal weight (EFW) < 3(rd) centile and absent end-diastolic flow in the umbilical artery (UA)) and four contributory parameters (AC or EFW < 10(th) centile combined with a pulsatility index (PI) > 95(th) centile in either the UA or uterine artery) were agreed upon. For late FGR (>/= 32 weeks), two solitary parameters (AC or EFW < 3(rd) centile) and four contributory parameters (EFW or AC < 10(th) centile, AC or EFW crossing centiles by > two quartiles on growth charts and cerebroplacental ratio < 5(th) centile or UA-PI > 95(th) centile) were defined. CONCLUSION: Consensus-based definitions for early and late FGR, as well as cut-off values for parameters involved, were agreed upon by a panel of experts. Copyright (c) 2016 ISUOG. Published by John Wiley & Sons Ltd.","author":[{"dropping-particle":"","family":"Gordijn","given":"S J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beune","given":"I M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Thilaganathan","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Papageorghiou","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Baschat","given":"A A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Baker","given":"P N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Silver","given":"R M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wynia","given":"K","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ganzevoort","given":"W","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound Obstet Gynecol","id":"ITEM-1","issue":"3","issued":{"date-parts":[["2016"]]},"note":"Gordijn, S J\nBeune, I M\nThilaganathan, B\nPapageorghiou, A\nBaschat, A A\nBaker, P N\nSilver, R M\nWynia, K\nGanzevoort, W\neng\nEngland\n2016/02/26 06:00\nUltrasound Obstet Gynecol. 2016 Sep;48(3):333-9. doi: 10.1002/uog.15884.","page":"333-339","title":"Consensus definition of fetal growth restriction: a Delphi procedure","type":"article-journal","volume":"48"},"uris":[""]}],"mendeley":{"formattedCitation":"(1)","plainTextFormattedCitation":"(1)","previouslyFormattedCitation":"(1)"},"properties":{"noteIndex":0},"schema":""}(1)). To capture the extreme cohort, inclusion criteria also included diagnosis prior to 28 weeks’ gestation, with delivery by or planned at 32 weeks’ gestation. EFW was calculated using Hadlock BPD-HC-AC-FL, as is currently standard in this unit.Data collected were as follows: maternal – demographic and antenatal booking data; fetal – gestational age at scan (based on first or second trimester ultrasound dating scan), biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), femur length (FL), umbilical artery Doppler end-diastolic flow (EDF), amniotic fluid index (AFI) and fetal presentation; pregnancy outcome – gestational age at delivery, birthweight, fetal sex. Twenty-one previously published sonographic fetal weight estimation models were identified from the literature, four of which were specific to SGA fetuses (Table 1)ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]},{"id":"ITEM-2","itemData":{"ISSN":"0278-4297","PMID":"8887237","abstract":"Most estimated fetal weight formulas have been derived and tested with larger fetuses, yet accuracy in predicting birth weight is more critical at the limit of viability. Complete data from 142 pregnancies in which delivery took place within 7 days of an ultrasonographic examination were used to create an appropriate formula for fetuses less than 1000 g and compare it with 10 currently available formulas. Our formula (In [BW] = 0.66 x 1n [HC] + 1.04 x 1n [AC] + 0.985 x 1n [FL]) was significantly more accurate than all other formulas and also performed better on a prospective cohort of 27 fetuses with estimated fetal weight less than 1000 g. Of the existing formulas, the Hadlock formula (using head circumference, abdominal circumference, femur length) was the most accurate, being significantly more accurate than all but the Woo formula with all but the Woo formula.","author":[{"dropping-particle":"","family":"Scott","given":"F","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beeby","given":"P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Abbott","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Edelman","given":"D","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Boogert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine","id":"ITEM-2","issue":"10","issued":{"date-parts":[["1996","10"]]},"page":"669-72","title":"New formula for estimating fetal weight below 1000 g: comparison with existing formulas.","type":"article-journal","volume":"15"},"uris":[""]},{"id":"ITEM-3","itemData":{"DOI":"10.1002/uog.1741","ISSN":"09607692","author":[{"dropping-particle":"","family":"Schild","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fell","given":"K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fimmers","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gembruch","given":"U.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hansmann","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-3","issue":"7","issued":{"date-parts":[["2004","12","1"]]},"page":"775-780","publisher":"John Wiley & Sons, Ltd","title":"A new formula for calculating weight in the fetus of ≤ 1600 g","type":"article-journal","volume":"24"},"uris":[""]},{"id":"ITEM-4","itemData":{"DOI":"10.1055/s-2007-963645","ISSN":"0172-4614","PMID":"19137495","abstract":"PURPOSE Birth weight is an important predictive parameter for neonatal morbidity and mortality in the small fetus. Accurate estimation of fetal weight is therefore a valuable tool for determining the further obstetric management. The majority of studies presenting new formulas have included relatively small samples with a narrow range of birth weights, mostly term fetuses. In a previous study, we evaluated several weight formulas over the whole range of birth weights and in defined subgroups. We were able to show that some regression formulas appeared to be favorable within these subgroups. Notably, the highest levels of inaccuracy were found in the group of infants with a birth weight of less than 2500 g. This led us to hypothesize that a formula based on the lower birth weight group might increase the accuracy of weight estimation. The aim of the present study was therefore to develop a new specific formula for estimating weight in fetuses less than or equal to 2500 g and to compare the new regression formula with commonly used weight equations. MATERIALS AND METHODS This study included 260 pregnancies. The inclusion criteria were a singleton pregnancy; birth weight equal to or less than 2500 g; an ultrasound examination with complete biometric parameters within 7 days prior to delivery; and an absence of structural or chromosomal malformations. The data for the first 130 newborns were used to develop a new formula. The remaining 130 infants were used to evaluate the new regression formula and to compare it to commonly used weight equations. Stepwise regression analysis was carried out with the birth weight as the dependent variable and biometric parameters as independent parameters to obtain the best-fit formula. RESULTS The mean absolute percentage error for the new formula was 7.71 %. Compared to the other formulas, it generated the highest intraclass correlation coefficient. By the limits of agreement, the new formula demonstrated only a slight tendency towards underestimating fetal weight, and it provided the smallest range of all weight equations. CONCLUSION With proper application, our new formula can improve the accuracy of fetal weight estimation.","author":[{"dropping-particle":"","family":"Siemer","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hilbert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hart","given":"N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Meurer","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Goecke","given":"T","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Schild","given":"R","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultraschall in der Medizin - European Journal of Ultrasound","id":"ITEM-4","issue":"01","issued":{"date-parts":[["2009","1","9"]]},"page":"47-51","title":"A New Sonographic Weight Formula for Fetuses?≤?2500 g","type":"article-journal","volume":"30"},"uris":[""]},{"id":"ITEM-5","itemData":{"DOI":"10.1016/0002-9378(83)91195-X","ISSN":"0002-9378","abstract":"Based on ultrasonographic mensuration, a number of equations have previously been devised for the purpose of estimating fetal weights. The objective of this study was to develop a mathematical equation that is simple, accurate, and easy to use when applied to preterm or low-birth weight fetuses (<2,500 gm). Real-time ultrasound measurements of fetal biparietal diameters (BPDs) and abdominal circumferences (ACs) were obtained in 62 pregnant women within one week of premature delivery. Mean gestational age and mean birth weight ± SD for this study group of neonates were 28.5 ± 3.5 weeks and 1,135 ± 343 gm, respectively. With the aid of computer analysis, a simple regression equation was derived: EFW = (BPD x AC x 9.337) ?299. When predicted estimated fetal weight (EFW) was compared with actual birth weight (ABW), multiple regression analysis demonstrated a correlation coefficient (R) of 0.957. Preliminary results on 19 oatients of a prospective study showed an absolute mean difference between the computed EFWs and the ABWs to be within 7.0% of ABW (70 gm/kg of ABW). The standard deviation of the difference was 9.3% of ABW (93 gm/kg of ABW). Based on these data, this simple equation appears to be clinically reliable and easy to use when estimating weights of preterm or low-birth weight fetuses of less than 2,500 gm.","author":[{"dropping-particle":"","family":"Thurnau","given":"Gary R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Tamura","given":"Ralph K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sabbagha","given":"Rudy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Depp","given":"O.Richard","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Dyer","given":"Alan","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Larkin","given":"Ron","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Lee","given":"Timothy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Laughlin","given":"Colby","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-5","issue":"5","issued":{"date-parts":[["1983","3","1"]]},"page":"557-561","publisher":"Mosby","title":"A simple estimated fetal weight equation based on real-time ultrasound measurements of fetuses less than thirty-four weeks' gestation","type":"article-journal","volume":"145"},"uris":[""]},{"id":"ITEM-6","itemData":{"ISSN":"0029-7844","PMID":"8355935","abstract":"OBJECTIVES To derive a formula for sonographic estimated fetal weight (EFW) based on a two-compartment model of fetal volume and to test it against two widely used formulas, especially at the extremes of fetal weight for which existing formulas are generally inaccurate. METHODS We analyzed 865 consecutive sonograms that met the following inclusion criteria: singleton pregnancy, normal anatomy, delivery within 3 days of sonography, and measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). The weight of the fetal head was modeled to be proportional to HC3, and the weight of the trunk proportional to AC2 x FL. The proportionality constants were found by multiple linear regression on 380 sonograms performed in 1990 (the \"derivation set\"). The new formula was tested for accuracy of prediction of actual birth weight against the formulas of Hadlock et al and Shepard et al using 485 sonograms from 1991-1992 (the \"validation set\"). RESULTS In the derivation set, the formula EFW = (0.23718 x AC2 x FL) + (0.03312 x HC3) was fit; the correlation with actual birth weight had an r value of 0.996. In the validation set, the new formula produced smaller systematic errors and smaller absolute errors than either the Hadlock or Shepard formula both overall and in fetal weight strata from less than 1000 g to over 4000 g. CONCLUSION The new formula makes geometric sense and provides accurate estimates of fetal weight across a broad range of weights.","author":[{"dropping-particle":"","family":"Combs","given":"C A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Jaekle","given":"R K","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Rosenn","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Pope","given":"M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Miodovnik","given":"M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Siddiqi","given":"T A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Obstetrics and gynecology","id":"ITEM-6","issue":"3","issued":{"date-parts":[["1993","9"]]},"page":"365-70","title":"Sonographic estimation of fetal weight based on a model of fetal volume.","type":"article-journal","volume":"82"},"uris":[""]},{"id":"ITEM-7","itemData":{"DOI":"10.1148/radiology.150.2.6691115","ISSN":"0033-8419","PMID":"6691115","abstract":"Sonographic estimation of fetal weight in utero was performed in 167 live-born fetuses examined within one week of delivery. Regression models were based on measurements of abdominal circumference, head circumference, biparietal diameter, and femur length, both alone and in combination. The best results (1 S.D. = 7.5% of actual weight) were obtained by combining measurements of the fetal head, abdomen, and femur, most likely due to the strong linear relationship between femur length and crown-heel length.","author":[{"dropping-particle":"","family":"Hadlock","given":"F P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Carpenter","given":"R J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R L","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"S K","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Radiology","id":"ITEM-7","issue":"2","issued":{"date-parts":[["1984","2","1"]]},"page":"535-40","title":"Sonographic estimation of fetal weight. The value of femur length in addition to head and abdomen measurements.","type":"article-journal","volume":"150"},"uris":[""]},{"id":"ITEM-8","itemData":{"DOI":"10.1055/s-2007-999885","ISSN":"0735-1631","author":[{"dropping-particle":"","family":"Ott","given":"William","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Doyle","given":"Sue","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Flamm","given":"Sandy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wittman","given":"Jackie","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Perinatology","id":"ITEM-8","issue":"04","issued":{"date-parts":[["1986","10","4"]]},"page":"307-310","publisher":"? 1986 by Thieme Medical Publishers, Inc.","title":"Accurate Ultrasonic Estimation of Fetal Weight","type":"article-journal","volume":"3"},"uris":[""]},{"id":"ITEM-9","itemData":{"DOI":"10.1016/S0002-9378(16)32283-9","ISSN":"0002-9378","abstract":"In an earlier study we presented a method of determining fetal weight from ultrasound measurements of abdominal circumference (AC) and biparietal diameter (BPD). From an equation with these two measurements as independent variables we generated tables of estimated fetal weights (E1). Although these tables have been very useful, we had the impression we were underestimating fetal weight. Therefore, we reconsidered an earlier unpublished table generated from a different equation (E2). While most estimates from E1 and E2 were likely to be within 10% of actual weight, there was significant underestimation with E1. E2 provides a better balance between the distribution of overestimations and underestimations.","author":[{"dropping-particle":"","family":"Shepard","given":"Mary Jo","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Richards","given":"Virginia A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Berkowitz","given":"Richard L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Warsof","given":"Steven L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hobbins","given":"John C.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-9","issue":"1","issued":{"date-parts":[["1982","1","1"]]},"page":"47-54","publisher":"Mosby","title":"An evaluation of two equations for predicting fetal weight by ultrasound","type":"article-journal","volume":"142"},"uris":[""]},{"id":"ITEM-10","itemData":{"DOI":"10.1016/0002-9378(77)90058-8","ISSN":"0002-9378","abstract":"The need for a quick and easy method for estimating fetal weight in utero has been clearly established. Estimates by abdominal palpation and fetal hormone production have proved to be of limited value. Eighty-five patients, ranging from 17 to 41 weeks' gestation, were ultrasonically scanned within 48 hours of delivery. Statistical analysis and multiple multivariant linear regressions were performed employing the BMD statistical packages. Our results show that birth weight is a logarithmic function of fetal body parameters and that the abdominal circumference has the single best correlation with the log10 birth weight. Our best linear regression with the use of two fetal dimensions (abdominal circumference and biparietal diameter) had a standard deviation of 106 grams per kilogram fetal weight. Since this derived formula is very cumbersome to manipulate, tables have been prepared with computer assistance to read the estimated fetal weight directly. Prospective estimates in 32 cases of both normal and pathologic gestations have proved to be within our expected accuracy.","author":[{"dropping-particle":"","family":"Warsof","given":"Steven L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gohari","given":"Parviz","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Berkowitz","given":"Richard L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hobbins","given":"John C.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-10","issue":"8","issued":{"date-parts":[["1977","8","15"]]},"page":"881-892","publisher":"Mosby","title":"The estimation of fetal weight by computer-assisted analysis","type":"article-journal","volume":"128"},"uris":[""]},{"id":"ITEM-11","itemData":{"ISSN":"0029-7844","PMID":"3515257","abstract":"Most published sonographic techniques for estimating fetal weight use measurements of the biparietal diameter (BPD) and abdominal circumference. In many clinical situations, however, accurate head measurements cannot be obtained. One hundred one patients were scanned within 72 hours of delivery. Using multiple stepwise regression analysis, a best-fit formula was developed using abdominal circumference and femur length, or femur length alone. The mean error was 109 g/kg fetal weight for abdominal circumference and femur length that was comparable with BPD and abdominal circumference formulas for estimated fetal weight. The mean error when femur length was used alone was 129 g/kg fetal weight. When these models were tested prospectively on 67 patients and compared with published formulas, they yielded results that were similar in accuracy. Among these additional patients, the model using one parameter (femur length) had an average error of 114 g/kg, whereas the femur length and abdominal circumference showed a mean error of 125 g/kg.","author":[{"dropping-particle":"","family":"Warsof","given":"S L","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wolf","given":"P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Coulehan","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Queenan","given":"J T","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Obstetrics and gynecology","id":"ITEM-11","issue":"4","issued":{"date-parts":[["1986","4"]]},"page":"569-73","title":"Comparison of fetal weight estimation formulas with and without head measurements.","type":"article-journal","volume":"67"},"uris":[""]},{"id":"ITEM-12","itemData":{"DOI":"10.7863/jum.1994.13.11.823","ISSN":"02784297","author":[{"dropping-particle":"","family":"Ferrero","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Maggi","given":"E","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Giancotti","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Torcia","given":"F","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Pachì","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of Ultrasound in Medicine","id":"ITEM-12","issue":"11","issued":{"date-parts":[["1994","11","1"]]},"page":"823-833","publisher":"John Wiley & Sons, Ltd","title":"Regression formula for estimation of fetal weight with use of abdominal circumference and femur length: a prospective study.","type":"article-journal","volume":"13"},"uris":[""]},{"id":"ITEM-13","itemData":{"ISSN":"0306-5456","PMID":"1101942","abstract":"A method of estimating fetal weight by ultrasonic measurement of the fetal abdominal circumference is descirbed. Assessment of birth weight predictions on 140 fetuses who were delivered within 48 hours of this measurement showed that the accuracy of predictions varied with the size of the fetus; at a predicted weight of 1 kg, 95 per cent of birth weights fell within 160 g, while at 2 kg, 3 kg and 4 kg the corresponding values were 290 g, 450 g and 590 g respectively. Expressed as a percentage of the predicted weight, confidence limits remained constant throughout the birth weight range. Extrapolation of these data to routine screening of the obstetric population showed that with a single measurement at 32 weeks menstrual age, 87 per cent of babies below the 5th centile would be detected by this method but that the diagnosis rate would fall to 63 per cent at 38 weeks. The false positive diagnosis rate would remain constant between 32 and 38 weeks at just over 1 per cent.","author":[{"dropping-particle":"","family":"Campbell","given":"S","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wilkin","given":"D","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"British journal of obstetrics and gynaecology","id":"ITEM-13","issue":"9","issued":{"date-parts":[["1975","9"]]},"page":"689-97","title":"Ultrasonic measurement of fetal abdomen circumference in the estimation of fetal weight.","type":"article-journal","volume":"82"},"uris":[""]},{"id":"ITEM-14","itemData":{"ISSN":"0306-5456","PMID":"1182089","abstract":"A new method of estimating fetal weight from the circumference of the fetal trunk, measured by ultrasound, is described. Comparison of weights estimated in this way with the actual birth weights of 50 fetuses, delivered not more than 48 hours later, shows a mean error in prediction of only 75 g, and in 94 per cent the error was less than 145 g. With such accuracy, the method is of clinical value, particularly in anticipating difficult delivery and in monitoring growth of the fetus at risk.","author":[{"dropping-particle":"","family":"Higginbottom","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Slater","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Porter","given":"G","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Whitfield","given":"C R","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"British journal of obstetrics and gynaecology","id":"ITEM-14","issue":"9","issued":{"date-parts":[["1975","9"]]},"page":"698-701","title":"Estimation of fetal weight from ultrasonic measurement of trunk circumference.","type":"article-journal","volume":"82"},"uris":[""]},{"id":"ITEM-15","itemData":{"DOI":"10.1002/uog.17347","ISSN":"14690705","abstract":"? 2016 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology. Objective: Estimated fetal weight (EFW) and fetal biometry are complementary measures used to screen for fetal growth disturbances. Our aim was to provide international EFW standards to complement the INTERGROWTH-21 st Fetal Growth Standards that are available for use worldwide. Methods: Women with an accurate gestational-age assessment, who were enrolled in the prospective, international, multicenter, population-based Fetal Growth Longitudinal Study (FGLS) and INTERBIO-21 st Fetal Study (FS), two components of the INTERGROWTH-21 st Project, had ultrasound scans every 5 weeks from 9–14 weeks' until 40 weeks' gestation. At each visit, measurements of fetal head circumference (HC), biparietal diameter, occipitofrontal diameter, abdominal circumference (AC) and femur length (FL) were obtained blindly by dedicated research sonographers using standardized methods and identical ultrasound machines. Birth weight was measured within 12 h of delivery by dedicated research anthropometrists using standardized methods and identical electronic scales. Live babies without any congenital abnormality, who were born within 14 days of the last ultrasound scan, were selected for inclusion. As most births occurred at around 40 weeks' gestation, we constructed a bootstrap model selection and estimation procedure based on resampling of the complete dataset under an approximately uniform distribution of birth weight, thus enriching the sample size at extremes of fetal sizes, to achieve consistent estimates across the full range of fetal weight. We constructed reference centiles using second-degree fractional polynomial models. Results: Of the overall population, 2404 babies were born within 14 days of the last ultrasound scan. Mean time between the last scan and birth was 7.7 (range, 0–14) days and was uniformly distributed. Birth weight was best estimated as a function of AC and HC (without FL) as log(EFW) = 5.084820 ? 54.06633 × (AC/100) 3 ? 95.80076 × (AC/100) 3 × log(AC/100) + 3.136370 × (HC/100), where EFW is in g and AC and HC are in cm. All other measures, gestational age, symphysis–fundus height, amniotic fluid indices and interactions between biometric measures and gestational age, were not retained in the selection process because they did not improve the prediction of EFW. 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O.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Andersen","given":"H. F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Abbott","given":"S. E.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Carter","given":"A. A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Algren","given":"H.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Rocco","given":"D. A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sorensen","given":"T. K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Enquobahrie","given":"D.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Waller","given":"S.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-15","issued":{"date-parts":[["2017"]]},"title":"International estimated fetal weight standards of the INTERGROWTH-21st Project","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(6,7,17–21,8–10,12–16)","manualFormatting":"(7-11, 13-22)","plainTextFormattedCitation":"(6,7,17–21,8–10,12–16)","previouslyFormattedCitation":"(7–11,13–22)"},"properties":{"noteIndex":0},"schema":""}(7-11, 13-22). These models are labelled 1-21 and will be referred to by their assigned number for the remainder of this manuscript.Statistical analysis of estimated fetal weight calculationThe EFW was calculated for each pregnancy in the cohort according to each model. This was used to calculate the error expressed as a percentage of the actual birthweight:Percentage error= EFW-birthweightbirthweight×100For each model, mean percentage error, (systematic error), was calculated as a measure of accuracy, and the standard deviation of the percentage error was used to calculate random error (random error = standard deviation of percentage error x 100), a measure of precision, and plotted for each model as a box and whisker plot. This was replicated with the cohort analysed according to gestational age, EFW, fetal presentation and fetal asymmetry, to determine if accuracy and precision were influenced by these parameters. Fetal asymmetry was defined as HC:AC ratio >95th centile for gestationADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1046/j.1469-0705.1994.04010034.x","ISSN":"14690705","abstract":"Normal ranges for a wide variety of biometrical parameters were established from cross‐sectional data on 1040 normal singleton pregnancies resulting in livebirth at term of normal, and appropriately grown infants. Patients were selected so that the birth weight distribution was similar to that reported by Yudkin and colleagues' and the ranges can, therefore, be used for any population that has a simular birth weight distribution. Copyright ? 1994 International Society of Ultrasound in Obstetrics and Gynecology Copyright ? 1994 International Society of Ultrasound in Obstetrics and Gynecology","author":[{"dropping-particle":"","family":"Snijders","given":"R. J M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Nicolaides","given":"K. H.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["1994"]]},"title":"Fetal biometry at 14–40 weeks' gestation","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(22)","plainTextFormattedCitation":"(22)","previouslyFormattedCitation":"(23)"},"properties":{"noteIndex":0},"schema":""}(22).To identify the best performing model, a scatter plot of systematic error against random error for each model was created. A perfect model would have systematic error of 0% and a random error of 0%, therefore models were ranked according to their distance from the origin, as a composite of the random and systematic errors using Pythagoras’ theorem: Distance from origin= Random error2+Systematic error2 ,the model with the smallest distance being the best performing. Scatter plots were then replotted with the cohort reanalysed according to gestation, EFW, fetal presentation and fetal asymmetry as described above, and cluster analysis used to determine if these parameters altered the model ranking. Calculated distances were then compared against each other (using Mann Whitney test to determine significance) to explore if these factors influenced the systematic and random errors.Using the best performing model, correlation coefficients (Pearson’s correlation) were calculated to determine how closely individual parameters within the model related to EFW. Regression analysis was applied to investigate the relationship between the mean percentage error of the best performing model for each case and gestational age at time of scan, EFW and AFI to determine if there was an association between the performance of the model and these continuous variables. Ethical approvalThis study has received HRA and NHS REC approval (West Midlands – Solihull Research Ethics Committee; 19/WM/0023). RESULTS159 cases of eFGR were identified in the specified time period. 94 were excluded as a growth scan was not performed within 48 hours of delivery, leaving 65 cases included in the final analysis. Characteristics of the entire eFGR cohort and the cohort selected for analysis are summarised in Table 2. The early gestational age at delivery (28.8 + 2.10 weeks), extremely low birthweight (716g (IQR 268g)) and survival to discharge rate of 77% reflect the extreme nature of the cohort investigated (Table 2). Of note, the median EFW was marginally higher than the median birthweight (722g compared to 717g), highlighting a tendency of the Hadlock BPD-HC-AC-FL model to overestimate fetal weight. Comparing general characteristics confirms that those who had a growth scan within 48 hours of delivery are representative of the overall eFGR cohort, with no significant differences in maternal age, BMI, ethnicity, parity, gestational age at delivery and birthweight (Table 2). It should be noted however that the pregnancy survival to discharge rates of the cases selected for this analysis (77%) are higher than that of the entire eFGR cohort (60%); this may reflect the nature of antenatal surveillance in this compromised group, with those fetuses that are too small/early in gestation to survive, or have very abnormal Doppler parameters, undergoing less frequent scans until they reach a point of viability.Overall, there was a wide variation in both accuracy and precision of the models investigated, with the systematic error having a median of 8.2% (range -44.1% – 49.5%) and a median random error of 11.6% (range 9.7% – 23.8%). The systematic and random errors of each model are summarised in Supporting Information (Table S1). Figure 1(a) summarises the systematic error (box) and random error (whisker) for each model across the overall cohort, and it appears that there is a tendency for overestimation of the EFW, regardless of the fetal parameters included in the model calculation or the original population used to develop the model (SGA or appropriately grown). When analysed by gestation (Figure 1(b)), EFW (Figure 1(c)), fetal presentation (Figure 1(d)) or asymmetry (Figure 1(e)), the pattern of overestimation/underestimation does not change, suggesting that none of these factors significantly impact model performance.Figure 2(a) shows the systematic error plotted against the random error for the overall cohort, and then by gestational age (Figure 2(b)), EFW (Figure 2(c)), fetal presentation (Figure 2(d)) or asymmetry (Figure 2(e)). Cluster analysis did not reveal any distinct clustering, suggesting that none of these parameters have a significant effect on the accuracy or the precision of the models investigated. By calculating the distance from each point to the origin of the graph, the top performing models were identified (the model with the smallest distance to origin taken to be the top performing model), and these are summarised in Table 3 (both by the overall cohort, and when the cohort is analysed by gestation/EFW/presentation/asymmetry). Model 2 (Hadlock HC-AC-FL) consistently performs the best regardless of gestational age, fetal presentation or asymmetry. When model performance was assessed according to EFW (less than or greater than/equal to 750g), Model 18 (Schild HC-AC-FL)ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.1741","ISSN":"09607692","author":[{"dropping-particle":"","family":"Schild","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fell","given":"K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fimmers","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gembruch","given":"U.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hansmann","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issue":"7","issued":{"date-parts":[["2004","12","1"]]},"page":"775-780","publisher":"John Wiley & Sons, Ltd","title":"A new formula for calculating weight in the fetus of ≤ 1600 g","type":"article-journal","volume":"24"},"uris":[""]}],"mendeley":{"formattedCitation":"(8)","plainTextFormattedCitation":"(8)","previouslyFormattedCitation":"(9)"},"properties":{"noteIndex":0},"schema":""}(8) performed better in those with an EFW > 750g; this model was specifically developed for SGA pregnancies in a cohort with a mean birthweight of 997g, similar to the subgroup investigated here.Figures 2 (c) and (d) suggest that there is a trend towards improved accuracy in those fetuses with an EFW less than 750g, and those in the breech position, as shown by the split in the groups which is starting to become apparent on the scatter graphs. However, when comparing the systematic error/random error/distance to the origin within the split cohort (Table 3 and Figure 2), there is no significant influence on model performance from gestational age, EFW or fetal presentation.The proportion of cases with EFW within 5-15% of actual birthweight were calculated for the top performing models (2, 1, 5 and 19) (Table 4). This highlights that even with the best performing model (Hadlock HC-AC-FL), only 64.6% of cases have an EFW within 10% of birthweight and in 14% of cases calculated EFW was more than 15% from measured birthweight.Table 5 displays correlation coefficients for each biometry measurement. Unsurprisingly, AC correlates most strongly with EFW (0.91), and FL has the weakest correlation (0.82). This is reflected in the model coefficients, with AC having the most influence on the calculated EFW.For Model 2 (the best performing model), linear regression analysis was used to investigate the continuous relationship between percentage error and gestational age at scan (Figure 3(a)), EFW (Figure 3(b)) and AFI (Figure 3(c)). There was no significant association between percentage error and gestational age at scan (P = 0.38, adjusted R2 = -0.003) or EFW (P = 0.13, adjusted R2 = 0.02), but there was a weak relationship with AFI (P = 0.02, adjusted R2 = 0.08). This suggests that at the lowest AFI, Model 2 tends to overestimate, and at the highest AFI it tends to underestimate fetal weight. DISCUSSIONWe have shown that in this eFGR cohort, Hadlock HC-AC-FL is consistently the best performing model for prediction of birthweight, independent of gestational age, EFW, AFI or fetal presentation. The accuracy and precision of the Hadlock (HC-AC-FL) model is a somewhat surprising finding, as this was derived from a cohort of 276 mixed gestational age fetuses, with a range of fetal weights and from a predominantly Caucasian populationADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6), whereas the cohort investigated here is much more ethnically diverse (less than 50% White European) and includes only pathologically small fetuses. Calculating the correlation coefficients of each biometry component within Hadlock HC-AC-FL shows that AC is most strongly correlated with EFW, and FL has the weakest association. However, when considering the biometry measurements included within the top five performing models assessed, all involved at least AC and FL, suggesting that inclusion of FL does improve precision and accuracy of EFW calculation, despite the presence/absence of asymmetric FGR. This contradicts previous work in a similar population that suggested that inclusion of FL in a severely growth-restricted population led to underestimation of fetal weight in asymmetric FGRADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.7605","ISSN":"09607692","abstract":"Objective To review the performance of a variety of biometry formulae for estimated fetal weight (EFW) in the management of severely growth restricted fetuses with abnormal umbilical artery Doppler at a single perinatal institution. Methods Forty-three pregnancies were retrospectively reviewed. Inclusion criteria were: chromosomally/ structurally normal fetus; complete ultrasound biometry at ≤7 days from delivery; EFW <10thcentile; absent/reversed end-diastolic flow in the umbilical arteries; and delivery at <32 + 6 weeks. EFW accuracy and precision were compared among nine formulae utilizing combinations of head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL) measurements. Results Twenty-six (60.5%) fetuses showed asymmetric growth (HC/AC ratio > 95thcentile). Analysis of the systematic and random errors associated with each formula showed that the birth weight of asymmetricallygrown fetuses was most closely approximated by the Hadlock equation that utilized BPD and AC measurements only. The birth weight of symmetrically-grown fetuses was most closely approximated by EFW derived from Hadlock equations that utilized ≥ three biometry measurements, including FL. Incorporation of FL into Hadlock formulae led to significant underestimation of birth weight in the fetuses with asymmetric growth (mean percentage error ± SD: EFWFL-AC, -13.3 ± 9.8%; EFWBPD-FL-AC, -10.8 ± 9.8%; EFWHC-FL-AC, -11.8 ± 9.3%; EFWBPD-HC-FL-AC, -11.7 ±} 9.5%; P < 0.001). The same equations were accurate in fetuses with symmetric growth (EFWFL-AC, 3.1 ± 10.0%; EFWBPD-FL-AC, 1.0 ± 8.9%; EFWHC-FL-AC, 0.3 ±) Copyright ? 2010 ISUOG. Published by John Wiley & Sons, Ltd.","author":[{"dropping-particle":"","family":"Proctor","given":"L. K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Rushworth","given":"V.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Shah","given":"P. S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Keunen","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Windrim","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ryan","given":"G.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kingdom","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2010"]]},"title":"Incorporation of femur length leads to underestimation of fetal weight in asymmetric preterm growth restriction","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(23)","plainTextFormattedCitation":"(23)","previouslyFormattedCitation":"(24)"},"properties":{"noteIndex":0},"schema":""}(23). The cohort studied in our analysis is similar to the population studied in that study in terms of gestational age and birthweight, but the calculated systematic errors for the Hadlock models in our study were closer to zero suggesting that overall, scanning in our study had improved accuracy, which may have overcome any error from FL inclusion.In addition to evaluating the performance of difference sonographic weight estimation models in eFGR as a whole, this study also sought to determine if different models perform better according to gestational age, fetal weight, fetal presentation or fetal asymmetry. Other than the SGA-specific model developed by Schild et al. which outperformed other models in those fetuses with an EFW>750g (likely because this subgroup closely represents the population that this particular model was developed inADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.1741","ISSN":"09607692","author":[{"dropping-particle":"","family":"Schild","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fell","given":"K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fimmers","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gembruch","given":"U.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hansmann","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issue":"7","issued":{"date-parts":[["2004","12","1"]]},"page":"775-780","publisher":"John Wiley & Sons, Ltd","title":"A new formula for calculating weight in the fetus of ≤ 1600 g","type":"article-journal","volume":"24"},"uris":[""]}],"mendeley":{"formattedCitation":"(8)","plainTextFormattedCitation":"(8)","previouslyFormattedCitation":"(9)"},"properties":{"noteIndex":0},"schema":""}(8)), the Hadlock HC-AC-FL model consistently performed the best. This implies that there is no benefit to selecting a different model to account for differences in gestation, fetal size, fetal presentation, asymmetry or AFI, as has been suggested previouslyADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.7863/ultra.15.02058","ISSN":"02784297","author":[{"dropping-particle":"","family":"Melamed","given":"Nir","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ryan","given":"Greg","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Windrim","given":"Rory","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Toi","given":"Ants","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kingdom","given":"John","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of Ultrasound in Medicine","id":"ITEM-1","issue":"1","issued":{"date-parts":[["2016","1","1"]]},"page":"71-82","publisher":"John Wiley & Sons, Ltd","title":"Choice of Formula and Accuracy of Fetal Weight Estimation in Small-for-Gestational-Age Fetuses","type":"article-journal","volume":"35"},"uris":[""]}],"mendeley":{"formattedCitation":"(11)","plainTextFormattedCitation":"(11)","previouslyFormattedCitation":"(12)"},"properties":{"noteIndex":0},"schema":""}(11). This may reflect the fact that as this was an extreme FGR cohort, it was a more homogenous population than other studies which have looked at SGA pregnancies, which will encompass a range of different pathologies, across a greater range of gestations and EFW. Interestingly, there is a non-significant trend towards improved performance in all models in those fetuses presenting breech and those fetuses with EFW<750g. This contradicts previous work suggesting the random error is larger in breech fetusesADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.8928","ISSN":"09607692","abstract":"OBJECTIVES: To assess the accuracy of sonographic weight estimation for fetuses in breech presentation, and to determine whether certain sonographic models perform better than others in cases of breech presentation.\\n\\nMETHODS: This was a retrospective cohort study of all sonographic weight estimations of fetuses in breech presentation performed within 3 days prior to delivery (n = 165). The accuracy of weight estimation was evaluated using eight sonographic models and was compared with a control group of fetuses in vertex presentation matched to the study group by birth weight and fetal gender (n = 165).\\n\\nRESULTS: After exclusion of a model based on femur diaphysis length alone, which was found to be highly inaccurate, the systematic error for fetuses in breech presentation was smaller than that observed for fetuses in vertex presentation (mean of all models - 0.14% vs. 2.0%, P = 0.01). The random error was higher in cases of breech presentation (9.4-13.2% vs. 7.5-8.9%, P < 0.05), and was lower for models that are based on three to four biometric indices (9.4-9.5%) compared with models that incorporate one to two biometric indices (10.8-13.6%, P < 0.05). Overall, the higher random error outweighed the decrease in the systematic error, as reflected by the lower fraction of weight estimations within 10% of birth weight among fetuses in breech presentation. Models based on three to four biometric indices were more accurate in detecting the weight thresholds beyond which a trial of vaginal delivery is usually not recommended.\\n\\nCONCLUSION: Sonographic weight estimation appears to be less accurate for fetuses in breech presentation, principally because of a larger random error. The use of sonographic models that are based on three to four biometric indices, training aimed at improving measurement in breech fetuses and the development of sonographic models derived from fetuses in breech presentation, may improve the accuracy of weight estimation in these cases.","author":[{"dropping-particle":"","family":"Melamed","given":"N.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ben-Haroush","given":"A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Meizner","given":"I.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Mashiach","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Yogev","given":"Y.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Pardo","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2011"]]},"title":"Accuracy of sonographic fetal weight estimation: A matter of presentation","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(24)","plainTextFormattedCitation":"(24)","previouslyFormattedCitation":"(25)"},"properties":{"noteIndex":0},"schema":""}(24). One explanation may be that in the breech position the fetal head can be more accurately approximated and is less influenced by physical compression from the uterine wall, as may occur in the cephalic position. Additionally, contrary to what is suggested by these results, it would be expected that ultrasound measurements in the smallest fetuses would be subject to a greater degree of error, and this has been confirmed previously by research which has shown reduced accuracy at extremes of birthweightADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.7863/jum.2009.28.5.617","ISSN":"02784297","abstract":"Objective. The purpose of this study was to compare the accuracy of different sonographic models for fetal weight estimation. Methods. We evaluated 26 different models using 3705 sonographic weight estimations performed less than 3 days before delivery. Models were ranked on the basis of systematic and random errors and were grouped according to the combination of biometric indices in each model. Cluster analysis was used to compare the accuracy of the different model groups. Results. A considerable variation in the accuracy of the different models was found. For birth weights (BWs) in the range of 1000 to 4500 g, models based on 3 or 4 fetal biometric indices were significantly more accurate than models that incorporated only 1 or 2 indices. The accuracy of weight estimation decreased at the extremes of BWs, leading to overestimation in low-BW categories as opposed to underestimation when the BW exceeded 4000 g. The precision of most models was lowest in the low-BW groups. Conclusions. To improve the accuracy of fetal weight estimation, sonographic models that are based on 3 or 4 fetal biometric indices should be preferred. Recognizing the accuracy and the tendency for underestimation or overestimation of each of the available models is important for the judicious interpretation of fetal weight estimations, especially at the extremes of fetal weight. ? 2009 by the American Institute of Ultrasound in Medicine.","author":[{"dropping-particle":"","family":"Melamed","given":"Nir","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Yogev","given":"Yariv","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Meizner","given":"Israel","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Mashiach","given":"Reuven","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Bardin","given":"Ron","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ben-Haroush","given":"Avi","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of Ultrasound in Medicine","id":"ITEM-1","issued":{"date-parts":[["2009"]]},"title":"Sonographic fetal weight estimation: Which model should be used?","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(25)","plainTextFormattedCitation":"(25)","previouslyFormattedCitation":"(26)"},"properties":{"noteIndex":0},"schema":""}(25). Our results may be in part due to examiner bias and awareness of the increased potential for error in measuring the smallest fetuses, subsequently leading to improved accuracy. There was weakly negative relationship between percentage error and AFI, which could have implications when interpreting EFW measurements in the context of oligohydramnios, often associated with eFGR. Practitioners should be aware that EFW in eFGR is more likely to be overestimated in the presence of oligohydramnios.The slight increase in performance in Hadlock HC-AC-FL compared to Hadlock BPD-HC-AC-FL confirms that addition of BPD does not offer any increase in accuracy or precision of EFW calculation, which is in keeping with previous studies which have shown the BPD actually explains little variance within the EFWADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.6317","ISSN":"09607692","abstract":"OBJECTIVES The main goal was to investigate the relationship between prenatal sonographic parameters and birth weight in predicting neonatal body composition. METHODS Standard fetal biometry and soft tissue parameters were assessed prospectively in third-trimester pregnancies using three-dimensional ultrasonography. Growth parameters included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), mid-thigh circumference and femoral diaphysis length (FDL). Soft tissue parameters included fractional arm volume (AVol) and fractional thigh volume (TVol) that were derived from 50% of the humeral or femoral diaphysis lengths, respectively. Percentage of neonatal body fat (%BF) was determined within 48 h of delivery using a pediatric air displacement plethysmography system based on principles of whole-body densitometry. Correlation and stepwise multiple linear regression analyses were performed with potential prenatal predictors and %BF as the outcome variable. RESULTS Eighty-seven neonates were studied with a mean +/- SD %BF of 10.6 +/- 4.6%. TVol had the greatest correlation with newborn %BF of all single-parameter models. This parameter alone explained 46.1% of the variability in %BF and the best stepwise multiple linear regression model was: %BF = 0.129 (TVol) - 1.03933 (P < 0.001). Birth weight similarly explained 44.7% of the variation in %BF. AC and estimated fetal weight (EFW) accounted for only 24.8% and 30.4% of the variance in %BF, respectively. Skeletal growth parameters, such as FDL (14.2%), HC (7.9%) and BPD (4.0%), contributed the least towards explaining the variance in %BF. CONCLUSIONS During the late third trimester of pregnancy %BF is most highly correlated with TVol. Similar to actual birth weight, this soft tissue parameter accounts for a significant improvement in explaining the variation in neonatal %BF compared with fetal AC or EFW alone.","author":[{"dropping-particle":"","family":"Lee","given":"W.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Balasubramaniam","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hassan","given":"S. S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gotsch","given":"F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kusanovic","given":"J. P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gon?alves","given":"L. F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Romero","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2009"]]},"title":"Fetal growth parameters and birth weight: Their relationship to neonatal body composition","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(26)","plainTextFormattedCitation":"(26)","previouslyFormattedCitation":"(27)"},"properties":{"noteIndex":0},"schema":""}(26). The systematic error is actually better for Hadlock BPD-HC-AC-FL than Hadlock HC-AC-FL (0.9 compared to 1.5), but the improved random error for Hadlock HC-AC-FL (9.7 compared to 10.0), means that overall this model performs slightly better. The margin of improvement gained from excluding BPD is minimal so it would be unreasonable to conclude that its inclusion is detrimental to EFW calculations. However, there does not appear to be any significant benefit, and time saved by not measuring the BPD could have implications in terms of scan time and efficiency. Although this study has shown that Hadlock HC-AC-FL remains the most accurate and precise model currently available for use in eFGR, there is a need for an improved model to reduce the number of cases where there is an error of more than 10% between estimated and actual birthweight. This model could either use routinely measured fetal biometry parameters utilised in the models discussed here, and be developed using a cohort of eFGR pregnancies, or incorporate alternative fetal biometry measurements. A potential area of interest is determining the effectiveness of three-dimensional thigh volume measurements in assessing fetal growthADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.7327","ISSN":"09607692","abstract":"OBJECTIVES The main goal of this study was to determine the accuracy and precision of new fetal weight estimation models, based on fractional limb volume and conventional two-dimensional (2D) sonographic measurements during the second and third trimesters of pregnancy. METHODS A prospective cross-sectional study of 271 fetuses was performed using three-dimensional ultrasonography to extract standard measurements-biparietal diameter (BPD), abdominal circumference (AC) and femoral diaphysis length (FDL)-plus fractional arm volume (AVol) and fractional thigh volume (TVol) within 4 days of delivery. Weighted multiple linear regression analysis was used to develop 'modified Hadlock' models and new models using transformed predictors that included soft tissue parameters for estimating birth weight. Estimated and observed birth weights were compared using mean percent difference (systematic weight estimation error) and the SD of the percent differences (random weight estimation error). The proportion of newborns with estimated birth weight within 5 or 10% of actual birth weight were compared using McNemar's test. RESULTS Birth weights in the study group ranged from 235 to 5790 g, with equal proportions of male and female infants. Six new fetal weight estimation models were compared with the results for modified Hadlock models with sample-specific coefficients. All the new models were very accurate, with mean percent differences that were not significantly different from zero. Model 3 (which used the natural logarithms of BPD, AC and AVol) and Model 6 (which used the natural logarithms of BPD, AC and TVol) provided the most precise weight estimations (random error = 6.6% of actual birth weight) as compared with 8.5% for the best original Hadlock model and 7.6% for a modified Hadlock model using sample-specific coefficients. Model 5 (which used the natural logarithms of AC and TVol) classified an additional 9.1% and 8.3% of the fetuses within 5% and 10% of actual birth weight and Model 6 classified an additional 7.3% and 4.1% of infants within 5% and 10% of actual birth weight. CONCLUSION The precision of fetal weight estimation can be improved by adding fractional limb volume measurements to conventional 2D biometry. New models that consider fractional limb volume may offer novel insight into the contribution of soft tissue development to weight estimation.","author":[{"dropping-particle":"","family":"Lee","given":"W.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Balasubramaniam","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Yeo","given":"L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hassan","given":"S. S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gotsch","given":"F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kusanovic","given":"J. P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gon?alves","given":"L. F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Romero","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2009"]]},"title":"New fetal weight estimation models using fractional limb volume","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(27)","plainTextFormattedCitation":"(27)","previouslyFormattedCitation":"(28)"},"properties":{"noteIndex":0},"schema":""}(27)ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.11185","ISSN":"09607692","author":[{"dropping-particle":"","family":"Lee","given":"W.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sangi-Haghpeykar","given":"H.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Yeo","given":"L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Romero","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics & Gynecology","id":"ITEM-1","issue":"2","issued":{"date-parts":[["2013","2","1"]]},"page":"198-203","publisher":"John Wiley & Sons, Ltd","title":"Prospective validation of fetal weight estimation using fractional limb volume","type":"article-journal","volume":"41"},"uris":[""]}],"mendeley":{"formattedCitation":"(28)","plainTextFormattedCitation":"(28)","previouslyFormattedCitation":"(29)"},"properties":{"noteIndex":0},"schema":""}(28). This has been explored in the context of detecting FGR in low risk pregnanciesADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/j.ajog.2017.06.018","ISSN":"10976868","abstract":"Background Currently, 2-dimensional ultrasound estimation of fetal size rather than fetal growth is used to define fetal growth restriction, but single estimates in late pregnancy lack sensitivity and may identify small for gestational age rather than growth restriction. Single or longitudinal measures of 3-dimensional fractional thigh volume may address this problem. Objective We sought to derive normal values for 3-dimensional fractional thigh volume in the third trimester, determine if fractional thigh volume is superior to 2-dimensional ultrasound biometry alone for detecting fetal growth restriction, and determine whether individualized growth assessment parameters have the potential to identify fetal growth restriction remote from term delivery. Study Design This was a longitudinal prospective cohort study of 115 unselected pregnancies in a tertiary referral unit (St Mary's Hospital, Manchester, United Kingdom). Standard 2-dimensional ultrasound biometry measurements were obtained, along with fractional thigh volume measurements (based on 50% of the femoral diaphysis length). Measurements were used to calculate estimated fetal weight (Hadlock). Individualized growth assessment parameters and percentage deviations in longitudinally measured biometrics were determined using a Web-based system (iGAP; ). Small for gestational age was defined <10th and fetal growth restriction <3rd customized birthweight centile. Logistic regression was used to compare estimated fetal weight (Hadlock), estimated fetal weight (biparietal diameter–abdominal circumference–fractional thigh volume), fractional thigh volume, and abdominal circumference for the prediction of small for gestational age or fetal growth restriction at birth. Screening performance was assessed using area under the receiver operating characteristic curve. Results There was a better correlation between fractional thigh volume and estimated fetal weight ((biparietal diameter–abdominal circumference–fractional thigh volume) obtained at 34-36 weeks with birthweight than between 2-dimensional biometry measures such as abdominal circumference and estimated fetal weight (Hadlock). There was also a modest improvement in the detection of both small for gestational age and fetal growth restriction using fractional thigh volume–derived measures compared to standard 2-dimensional measurements (area under receiver operating characteristic curve, 0.86; 95% confidence interval, 0.79–0.…","author":[{"dropping-particle":"","family":"Simcox","given":"Louise E.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Myers","given":"Jenny E.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Cole","given":"Tim J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Johnstone","given":"Edward D.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issued":{"date-parts":[["2017"]]},"title":"Fractional fetal thigh volume in the prediction of normal and abnormal fetal growth during the third trimester of pregnancy","type":"article-journal"},"uris":[""]}],"mendeley":{"formattedCitation":"(29)","plainTextFormattedCitation":"(29)","previouslyFormattedCitation":"(30)"},"properties":{"noteIndex":0},"schema":""}(29), but its ability to accurately predict fetal weight in a cohort of FGR, and specifically eFGR, remains unknown. There are several strengths to this study. Firstly, by including an extreme cohort of early FGR, we have studied a relatively homogenous population. Secondly, the maximum scan to delivery interval was 48 hours, meaning that EFW will have been an accurate representation of birthweight. Thirdly, birthweight was measured independently of EFW, so the birthweight measurement will not have been biased by the last EFW result. Lastly, cases studied were from a small number of translational research antenatal clinics, with a small number of sonographers. The main limitation lies in the number of cases analysed; 65 is comparable with other similar studies, however it is not large enough to develop and test a new sonographic weight estimation model, and any model developed will be overfitted to this data. CONCLUSIONThis study has confirmed that despite differences in the characteristics of the eFGR population compared to the population used to develop the Hadlock sonographic modelsADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]},{"id":"ITEM-2","itemData":{"DOI":"10.1148/radiology.150.2.6691115","ISSN":"0033-8419","PMID":"6691115","abstract":"Sonographic estimation of fetal weight in utero was performed in 167 live-born fetuses examined within one week of delivery. Regression models were based on measurements of abdominal circumference, head circumference, biparietal diameter, and femur length, both alone and in combination. The best results (1 S.D. = 7.5% of actual weight) were obtained by combining measurements of the fetal head, abdomen, and femur, most likely due to the strong linear relationship between femur length and crown-heel length.","author":[{"dropping-particle":"","family":"Hadlock","given":"F P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Carpenter","given":"R J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R L","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"S K","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Radiology","id":"ITEM-2","issue":"2","issued":{"date-parts":[["1984","2","1"]]},"page":"535-40","title":"Sonographic estimation of fetal weight. The value of femur length in addition to head and abdomen measurements.","type":"article-journal","volume":"150"},"uris":[""]}],"mendeley":{"formattedCitation":"(6,13)","plainTextFormattedCitation":"(6,13)","previouslyFormattedCitation":"(7,19)"},"properties":{"noteIndex":0},"schema":""}(6,13), there is currently no better performing model to accurately calculate EFW in eFGR. This study does not support the use of different models depending on different pregnancy conditions but suggests a tendency of the model to overestimate fetal weight at lower amniotic fluid levels. It has also highlighted that for 35% of eFGR pregnancies, the percentage error is more than 10% of the actual birthweight. This demonstrates the need for an improved model of EFW calculation in eFGR - at an EFW of 600g, a 10% error of 60g could significantly influence the decision to deliver, and subsequently impact on stillbirth risk/risk of neonatal mortality and morbidity. Whether an improved model would incorporate newer methods of fetal weight estimation, such as three-dimensional measurements, or be developed using standard biometry measurements in an eFGR population will form the focus of future work in this area.ACKNOWLEDGEMENTSThe authors would like to acknowledge the following contributions to this manuscript: Tommy’s Charity; the women attending the translational research clinics at St Mary’s Hospital, Manchester, UK; the clinicians and midwives working within these clinics.TWEETABLE ABSTRACTHadlock HC-AC-FL is the best available EFW model for early-onset FGR, but with only 2/3 of cases having an EFW within 10% of birthweight, improved models are needed.REFERENCESADDIN Mendeley Bibliography CSL_BIBLIOGRAPHY 1. Gordijn SJ, Beune IM, Thilaganathan B, Papageorghiou A, Baschat AA, Baker PN, et al. Consensus definition of fetal growth restriction: a Delphi procedure. Ultrasound Obs Gynecol [Internet]. 2016;48(3):333–9. Available from: . Mifsud W, Sebire NJ. Placental pathology in early-onset and late-onset fetal growth restriction. Fetal Diagn Ther [Internet]. 2014;36(2):117–28. Available from: . Sharp A, Cornforth C, Jackson R, Harrold J, Turner MA, Kenny LC, et al. Maternal sildenafil for severe fetal growth restriction (STRIDER): a multicentre, randomised, placebo-controlled, double-blind trial. Lancet Child Adolesc Heal [Internet]. 2017 Dec 1 [cited 2018 Jan 22];2(2):93–102. Available from: . Santhakumaran S, Statnikov Y, Gray D, Battersby C, Ashby D, Modi N, et al. Survival of very preterm infants admitted to neonatal care in England 2008-2014: time trends and regional variation. Arch Dis Child Fetal Neonatal Ed [Internet]. 2018 May 1 [cited 2019 Sep 30];103(3):F208–15. Available from: . Gardosi J. Fetal growth: Towards an international standard. Ultrasound in Obstetrics and Gynecology. 2005. 6. Hadlock FP, Harrist RB, Sharman RS, Deter RL, Park SK. Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study. Am J Obstet Gynecol [Internet]. 1985 Feb 1 [cited 2019 Jan 4];151(3):333–7. Available from: . Scott F, Beeby P, Abbott J, Edelman D, Boogert A. New formula for estimating fetal weight below 1000 g: comparison with existing formulas. J Ultrasound Med [Internet]. 1996 Oct [cited 2019 Jan 4];15(10):669–72. Available from: . Schild RL, Fell K, Fimmers R, Gembruch U, Hansmann M. A new formula for calculating weight in the fetus of ≤ 1600 g. Ultrasound Obstet Gynecol [Internet]. 2004 Dec 1 [cited 2019 Jan 4];24(7):775–80. Available from: . Siemer J, Hilbert A, Hart N, Meurer B, Goecke T, Schild R. A New Sonographic Weight Formula for Fetuses?≤?2500 g. Ultraschall der Medizin - Eur J Ultrasound [Internet]. 2009 Jan 9 [cited 2019 Jan 4];30(01):47–51. Available from: . Thurnau GR, Tamura RK, Sabbagha R, Depp OR, Dyer A, Larkin R, et al. A simple estimated fetal weight equation based on real-time ultrasound measurements of fetuses less than thirty-four weeks’ gestation. Am J Obstet Gynecol [Internet]. 1983 Mar 1 [cited 2019 Jan 4];145(5):557–61. Available from: . Melamed N, Ryan G, Windrim R, Toi A, Kingdom J. Choice of Formula and Accuracy of Fetal Weight Estimation in Small-for-Gestational-Age Fetuses. J Ultrasound Med [Internet]. 2016 Jan 1 [cited 2019 Jan 4];35(1):71–82. Available from: . Combs CA, Jaekle RK, Rosenn B, Pope M, Miodovnik M, Siddiqi TA. Sonographic estimation of fetal weight based on a model of fetal volume. Obstet Gynecol [Internet]. 1993 Sep [cited 2019 Jan 4];82(3):365–70. Available from: . Hadlock FP, Harrist RB, Carpenter RJ, Deter RL, Park SK. Sonographic estimation of fetal weight. The value of femur length in addition to head and abdomen measurements. Radiology [Internet]. 1984 Feb 1 [cited 2019 Jan 4];150(2):535–40. Available from: . Ott W, Doyle S, Flamm S, Wittman J. Accurate Ultrasonic Estimation of Fetal Weight. Am J Perinatol [Internet]. 1986 Oct 4 [cited 2019 Jan 4];3(04):307–10. Available from: . Shepard MJ, Richards VA, Berkowitz RL, Warsof SL, Hobbins JC. An evaluation of two equations for predicting fetal weight by ultrasound. Am J Obstet Gynecol [Internet]. 1982 Jan 1 [cited 2019 Jan 4];142(1):47–54. Available from: . Warsof SL, Gohari P, Berkowitz RL, Hobbins JC. The estimation of fetal weight by computer-assisted analysis. Am J Obstet Gynecol [Internet]. 1977 Aug 15 [cited 2019 Jan 4];128(8):881–92. Available from: . Warsof SL, Wolf P, Coulehan J, Queenan JT. Comparison of fetal weight estimation formulas with and without head measurements. Obstet Gynecol [Internet]. 1986 Apr [cited 2019 Jan 4];67(4):569–73. Available from: . Ferrero A, Maggi E, Giancotti A, Torcia F, Pachì A. Regression formula for estimation of fetal weight with use of abdominal circumference and femur length: a prospective study. J Ultrasound Med [Internet]. 1994 Nov 1 [cited 2019 Jan 4];13(11):823–33. Available from: . Campbell S, Wilkin D. Ultrasonic measurement of fetal abdomen circumference in the estimation of fetal weight. Br J Obstet Gynaecol [Internet]. 1975 Sep [cited 2019 Jan 4];82(9):689–97. Available from: . Higginbottom J, Slater J, Porter G, Whitfield CR. Estimation of fetal weight from ultrasonic measurement of trunk circumference. Br J Obstet Gynaecol [Internet]. 1975 Sep [cited 2019 Jan 4];82(9):698–701. Available from: . Stirnemann J, Villar J, Salomon LJ, Ohuma E, Ruyan P, Altman DG, et al. International estimated fetal weight standards of the INTERGROWTH-21st Project. Ultrasound Obstet Gynecol. 2017; 22. Snijders RJM, Nicolaides KH. Fetal biometry at 14–40 weeks’ gestation. Ultrasound Obstet Gynecol. 1994; 23. Proctor LK, Rushworth V, Shah PS, Keunen J, Windrim R, Ryan G, et al. Incorporation of femur length leads to underestimation of fetal weight in asymmetric preterm growth restriction. Ultrasound Obstet Gynecol. 2010; 24. Melamed N, Ben-Haroush A, Meizner I, Mashiach R, Yogev Y, Pardo J. Accuracy of sonographic fetal weight estimation: A matter of presentation. Ultrasound Obstet Gynecol. 2011; 25. Melamed N, Yogev Y, Meizner I, Mashiach R, Bardin R, Ben-Haroush A. Sonographic fetal weight estimation: Which model should be used? J Ultrasound Med. 2009; 26. Lee W, Balasubramaniam M, Deter RL, Hassan SS, Gotsch F, Kusanovic JP, et al. Fetal growth parameters and birth weight: Their relationship to neonatal body composition. Ultrasound Obstet Gynecol. 2009; 27. Lee W, Balasubramaniam M, Deter RL, Yeo L, Hassan SS, Gotsch F, et al. New fetal weight estimation models using fractional limb volume. Ultrasound Obstet Gynecol. 2009; 28. Lee W, Deter R, Sangi-Haghpeykar H, Yeo L, Romero R. Prospective validation of fetal weight estimation using fractional limb volume. Ultrasound Obstet Gynecol [Internet]. 2013 Feb 1 [cited 2019 Aug 21];41(2):198–203. Available from: . Simcox LE, Myers JE, Cole TJ, Johnstone ED. Fractional fetal thigh volume in the prediction of normal and abnormal fetal growth during the third trimester of pregnancy. Am J Obstet Gynecol. 2017; FIGURE LEGENDSFigure 1: Mean systematic error (box) and random error (whiskers) for each sonographic weight estimation model identified in Table 1. The blue line represents a systematic error of 0; models plotting above the line show overestimation, models plotting below this line show underestimation of the fetal weight. (a) Entire cohort; (b) Cohort split by gestational age at scan (pre/post 28 weeks’ gestation); (c) Cohort split by estimated fetal weight at scan (above/below 750g); (d) Cohort split by fetal presentation at scan; (e) Cohort split by symmetrical/asymmetrical FGR.Figure 2: Systematic error plotted against random error for models 1-21. Red lines denote systematic error and random error of 0%. Number and colour denote model number as shown in figure legend. (a) Entire cohort; (b) Cohort split by gestational age at scan (pre/post 28 weeks’ gestation); (c) Cohort split by estimated fetal weight at scan (above/below 750g); (d) Cohort split by fetal presentation at scan; (e) Cohort split by symmetrical/asymmetrical FGR.Figure 3: Model 2 percentage error against (a) gestational age at time of scan for each case (n=65) using Model 2. Regression analysis confirms that there is no relationship between the two (P = 0.38), suggesting that the percentage error does not change with gestation; (b) EFW for each case (n=65) using Model 2. Regression analysis confirms that there is no relationship between the two (P = 0.13), suggesting that the degree of error is not related to the actual fetal size in eFGR; (c) AFI at time of scan for each case (n=53) using Model 2. Regression analysis confirms an inverse association between the two (P < 0.05), so a low AFI will tend towards overestimation of the fetal weight, and a high AFI will tend towards underestimation of the fetal weight.TABLESTable SEQ Table \* ARABIC 1: EFW formulas used in analysisModel numberEquationReferenceBPD, HC, AC, FL1Log EFW (g) = 1.3596 + 0.0064*HC + 0.0424*AC 0.174*FL + 0.00061*BPD*AC - 0.00386*AC*FLHadlock, 1985 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6)HC, AC, FL2Log EFW (g) = 1.326 - 0.00326*AC*FL + 0.0107*HC + 0.0438*AC + 0.158*FLHadlock, 1985 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6) 3Ln EFW (g) = 0.04355*HC + 0.05394*AC - 0.0008582*HC*AC + 1.2594*(FL/AC) - 2.0661Ott, 1986 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1055/s-2007-999885","ISSN":"0735-1631","author":[{"dropping-particle":"","family":"Ott","given":"William","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Doyle","given":"Sue","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Flamm","given":"Sandy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wittman","given":"Jackie","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Perinatology","id":"ITEM-1","issue":"04","issued":{"date-parts":[["1986","10","4"]]},"page":"307-310","publisher":"? 1986 by Thieme Medical Publishers, Inc.","title":"Accurate Ultrasonic Estimation of Fetal Weight","type":"article-journal","volume":"3"},"uris":[""]}],"mendeley":{"formattedCitation":"(14)","plainTextFormattedCitation":"(14)","previouslyFormattedCitation":"(20)"},"properties":{"noteIndex":0},"schema":""}(14)4Log EFW (g) = 0.23718*AC2*FL + 0.03312*HC3Combs, 1993 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"ISSN":"0029-7844","PMID":"8355935","abstract":"OBJECTIVES To derive a formula for sonographic estimated fetal weight (EFW) based on a two-compartment model of fetal volume and to test it against two widely used formulas, especially at the extremes of fetal weight for which existing formulas are generally inaccurate. METHODS We analyzed 865 consecutive sonograms that met the following inclusion criteria: singleton pregnancy, normal anatomy, delivery within 3 days of sonography, and measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). The weight of the fetal head was modeled to be proportional to HC3, and the weight of the trunk proportional to AC2 x FL. The proportionality constants were found by multiple linear regression on 380 sonograms performed in 1990 (the \"derivation set\"). The new formula was tested for accuracy of prediction of actual birth weight against the formulas of Hadlock et al and Shepard et al using 485 sonograms from 1991-1992 (the \"validation set\"). RESULTS In the derivation set, the formula EFW = (0.23718 x AC2 x FL) + (0.03312 x HC3) was fit; the correlation with actual birth weight had an r value of 0.996. In the validation set, the new formula produced smaller systematic errors and smaller absolute errors than either the Hadlock or Shepard formula both overall and in fetal weight strata from less than 1000 g to over 4000 g. CONCLUSION The new formula makes geometric sense and provides accurate estimates of fetal weight across a broad range of weights.","author":[{"dropping-particle":"","family":"Combs","given":"C A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Jaekle","given":"R K","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Rosenn","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Pope","given":"M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Miodovnik","given":"M","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Siddiqi","given":"T A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Obstetrics and gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1993","9"]]},"page":"365-70","title":"Sonographic estimation of fetal weight based on a model of fetal volume.","type":"article-journal","volume":"82"},"uris":[""]}],"mendeley":{"formattedCitation":"(12)","plainTextFormattedCitation":"(12)","previouslyFormattedCitation":"(18)"},"properties":{"noteIndex":0},"schema":""}(12)BPD, AC, FL5Log EFW (g) = 1.335 - 0.0034*AC*FL + 0.0316*BPD + 0.0457*AC + 0.1623*FLHadlock, 1985 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6)BPD, AC6Log EFW (g) = 1.1134 + 0.05845*AC - 0.000604*AC2 - 0.007365*BPD2 + 0.000595*BPD*AC + 0.1694*BPDHadlock, 1984 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1148/radiology.150.2.6691115","ISSN":"0033-8419","PMID":"6691115","abstract":"Sonographic estimation of fetal weight in utero was performed in 167 live-born fetuses examined within one week of delivery. Regression models were based on measurements of abdominal circumference, head circumference, biparietal diameter, and femur length, both alone and in combination. The best results (1 S.D. = 7.5% of actual weight) were obtained by combining measurements of the fetal head, abdomen, and femur, most likely due to the strong linear relationship between femur length and crown-heel length.","author":[{"dropping-particle":"","family":"Hadlock","given":"F P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Carpenter","given":"R J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"R L","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"S K","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Radiology","id":"ITEM-1","issue":"2","issued":{"date-parts":[["1984","2","1"]]},"page":"535-40","title":"Sonographic estimation of fetal weight. The value of femur length in addition to head and abdomen measurements.","type":"article-journal","volume":"150"},"uris":[""]}],"mendeley":{"formattedCitation":"(13)","plainTextFormattedCitation":"(13)","previouslyFormattedCitation":"(19)"},"properties":{"noteIndex":0},"schema":""}(13)7Log EFW (g) = -1.599 + 0.144*BPD + 0.032*AC - 0.000111*BPD2*ACWarsof, 1977 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(77)90058-8","ISSN":"0002-9378","abstract":"The need for a quick and easy method for estimating fetal weight in utero has been clearly established. Estimates by abdominal palpation and fetal hormone production have proved to be of limited value. Eighty-five patients, ranging from 17 to 41 weeks' gestation, were ultrasonically scanned within 48 hours of delivery. Statistical analysis and multiple multivariant linear regressions were performed employing the BMD statistical packages. Our results show that birth weight is a logarithmic function of fetal body parameters and that the abdominal circumference has the single best correlation with the log10 birth weight. Our best linear regression with the use of two fetal dimensions (abdominal circumference and biparietal diameter) had a standard deviation of 106 grams per kilogram fetal weight. Since this derived formula is very cumbersome to manipulate, tables have been prepared with computer assistance to read the estimated fetal weight directly. Prospective estimates in 32 cases of both normal and pathologic gestations have proved to be within our expected accuracy.","author":[{"dropping-particle":"","family":"Warsof","given":"Steven L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gohari","given":"Parviz","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Berkowitz","given":"Richard L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hobbins","given":"John C.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"8","issued":{"date-parts":[["1977","8","15"]]},"page":"881-892","publisher":"Mosby","title":"The estimation of fetal weight by computer-assisted analysis","type":"article-journal","volume":"128"},"uris":[""]}],"mendeley":{"formattedCitation":"(16)","plainTextFormattedCitation":"(16)","previouslyFormattedCitation":"(22)"},"properties":{"noteIndex":0},"schema":""}(16)8Log EFW (g) = -1.7492 + 0.166*BPD + 0.046*AC - 0.002546*AC*BPDShepard, 1982 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/S0002-9378(16)32283-9","ISSN":"0002-9378","abstract":"In an earlier study we presented a method of determining fetal weight from ultrasound measurements of abdominal circumference (AC) and biparietal diameter (BPD). From an equation with these two measurements as independent variables we generated tables of estimated fetal weights (E1). Although these tables have been very useful, we had the impression we were underestimating fetal weight. Therefore, we reconsidered an earlier unpublished table generated from a different equation (E2). While most estimates from E1 and E2 were likely to be within 10% of actual weight, there was significant underestimation with E1. E2 provides a better balance between the distribution of overestimations and underestimations.","author":[{"dropping-particle":"","family":"Shepard","given":"Mary Jo","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Richards","given":"Virginia A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Berkowitz","given":"Richard L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Warsof","given":"Steven L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hobbins","given":"John C.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"1","issued":{"date-parts":[["1982","1","1"]]},"page":"47-54","publisher":"Mosby","title":"An evaluation of two equations for predicting fetal weight by ultrasound","type":"article-journal","volume":"142"},"uris":[""]}],"mendeley":{"formattedCitation":"(15)","plainTextFormattedCitation":"(15)","previouslyFormattedCitation":"(21)"},"properties":{"noteIndex":0},"schema":""}(15)AC, FL9Log EFW (g) = 1.304 + 0.05281*AC + 0.1938*FL - 0.004*AC*FLHadlock, 1985 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(85)90298-4","ISSN":"0002-9378","abstract":"In utero estimates of fetal weight were evaluated prospectively in 109 fetuses with the use of sonographic models developed in a previous study. This report confirms that the best in utero weight estimates result from the use of models based on measurements of head size, abdominal size, and femur length. Since the accuracy of these models (1 SD = 7.5%) is significantly better than those based on measurements of head and body (e.g., biparietal diameter, abdominal circumference), we recommend routine use of such models in obstetric sonography.","author":[{"dropping-particle":"","family":"Hadlock","given":"Frank P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Harrist","given":"R.B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sharman","given":"Ralph S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deter","given":"Russell L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Park","given":"Seung K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"3","issued":{"date-parts":[["1985","2","1"]]},"page":"333-337","publisher":"Mosby","title":"Estimation of fetal weight with the use of head, body, and femur measurements—A prospective study","type":"article-journal","volume":"151"},"uris":[""]}],"mendeley":{"formattedCitation":"(6)","plainTextFormattedCitation":"(6)","previouslyFormattedCitation":"(7)"},"properties":{"noteIndex":0},"schema":""}(6)10Ln EFW (g) = 2.792 + 0.108*FL + 0.0036*AC2 - 0.0027*FL*ACWarsof, 1986 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"ISSN":"0029-7844","PMID":"3515257","abstract":"Most published sonographic techniques for estimating fetal weight use measurements of the biparietal diameter (BPD) and abdominal circumference. In many clinical situations, however, accurate head measurements cannot be obtained. One hundred one patients were scanned within 72 hours of delivery. Using multiple stepwise regression analysis, a best-fit formula was developed using abdominal circumference and femur length, or femur length alone. The mean error was 109 g/kg fetal weight for abdominal circumference and femur length that was comparable with BPD and abdominal circumference formulas for estimated fetal weight. The mean error when femur length was used alone was 129 g/kg fetal weight. When these models were tested prospectively on 67 patients and compared with published formulas, they yielded results that were similar in accuracy. Among these additional patients, the model using one parameter (femur length) had an average error of 114 g/kg, whereas the femur length and abdominal circumference showed a mean error of 125 g/kg.","author":[{"dropping-particle":"","family":"Warsof","given":"S L","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wolf","given":"P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Coulehan","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Queenan","given":"J T","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Obstetrics and gynecology","id":"ITEM-1","issue":"4","issued":{"date-parts":[["1986","4"]]},"page":"569-73","title":"Comparison of fetal weight estimation formulas with and without head measurements.","type":"article-journal","volume":"67"},"uris":[""]}],"mendeley":{"formattedCitation":"(17)","plainTextFormattedCitation":"(17)","previouslyFormattedCitation":"(13)"},"properties":{"noteIndex":0},"schema":""}(17)11Ln EFW (g) = 0.77125 + 0.13244*AC - 0.12996*FL - 1.73588*AC2/1000 + 3.09212*FL*AC/1000 + 2.18984(FL/AC)Ferrero, 1994 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.7863/jum.1994.13.11.823","ISSN":"02784297","author":[{"dropping-particle":"","family":"Ferrero","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Maggi","given":"E","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Giancotti","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Torcia","given":"F","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Pachì","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of Ultrasound in Medicine","id":"ITEM-1","issue":"11","issued":{"date-parts":[["1994","11","1"]]},"page":"823-833","publisher":"John Wiley & Sons, Ltd","title":"Regression formula for estimation of fetal weight with use of abdominal circumference and femur length: a prospective study.","type":"article-journal","volume":"13"},"uris":[""]}],"mendeley":{"formattedCitation":"(18)","plainTextFormattedCitation":"(18)","previouslyFormattedCitation":"(14)"},"properties":{"noteIndex":0},"schema":""}(18)HC, AC12Log EFW (g) = 5.084820 – 54.06633*AC3 – 95.80076 * AC3 * log10(AC) + 3.136370 * HC Stirnemann, 2017 ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.17347","ISSN":"14690705","abstract":"? 2016 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology. Objective: Estimated fetal weight (EFW) and fetal biometry are complementary measures used to screen for fetal growth disturbances. Our aim was to provide international EFW standards to complement the INTERGROWTH-21 st Fetal Growth Standards that are available for use worldwide. Methods: Women with an accurate gestational-age assessment, who were enrolled in the prospective, international, multicenter, population-based Fetal Growth Longitudinal Study (FGLS) and INTERBIO-21 st Fetal Study (FS), two components of the INTERGROWTH-21 st Project, had ultrasound scans every 5 weeks from 9–14 weeks' until 40 weeks' gestation. At each visit, measurements of fetal head circumference (HC), biparietal diameter, occipitofrontal diameter, abdominal circumference (AC) and femur length (FL) were obtained blindly by dedicated research sonographers using standardized methods and identical ultrasound machines. Birth weight was measured within 12 h of delivery by dedicated research anthropometrists using standardized methods and identical electronic scales. Live babies without any congenital abnormality, who were born within 14 days of the last ultrasound scan, were selected for inclusion. As most births occurred at around 40 weeks' gestation, we constructed a bootstrap model selection and estimation procedure based on resampling of the complete dataset under an approximately uniform distribution of birth weight, thus enriching the sample size at extremes of fetal sizes, to achieve consistent estimates across the full range of fetal weight. We constructed reference centiles using second-degree fractional polynomial models. Results: Of the overall population, 2404 babies were born within 14 days of the last ultrasound scan. Mean time between the last scan and birth was 7.7 (range, 0–14) days and was uniformly distributed. Birth weight was best estimated as a function of AC and HC (without FL) as log(EFW) = 5.084820 ? 54.06633 × (AC/100) 3 ? 95.80076 × (AC/100) 3 × log(AC/100) + 3.136370 × (HC/100), where EFW is in g and AC and HC are in cm. All other measures, gestational age, symphysis–fundus height, amniotic fluid indices and interactions between biometric measures and gestational age, were not retained in the selection process because they did not improve the prediction of EFW. Applying the f…","author":[{"dropping-particle":"","family":"Stirnemann","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Villar","given":"J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Salomon","given":"L. J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ohuma","given":"E.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Ruyan","given":"P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Altman","given":"D. 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Complete data from 142 pregnancies in which delivery took place within 7 days of an ultrasonographic examination were used to create an appropriate formula for fetuses less than 1000 g and compare it with 10 currently available formulas. Our formula (In [BW] = 0.66 x 1n [HC] + 1.04 x 1n [AC] + 0.985 x 1n [FL]) was significantly more accurate than all other formulas and also performed better on a prospective cohort of 27 fetuses with estimated fetal weight less than 1000 g. Of the existing formulas, the Hadlock formula (using head circumference, abdominal circumference, femur length) was the most accurate, being significantly more accurate than all but the Woo formula with all but the Woo formula.","author":[{"dropping-particle":"","family":"Scott","given":"F","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beeby","given":"P","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Abbott","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Edelman","given":"D","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Boogert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine","id":"ITEM-1","issue":"10","issued":{"date-parts":[["1996","10"]]},"page":"669-72","title":"New formula for estimating fetal weight below 1000 g: comparison with existing formulas.","type":"article-journal","volume":"15"},"uris":[""]}],"mendeley":{"formattedCitation":"(7)","plainTextFormattedCitation":"(7)","previouslyFormattedCitation":"(8)"},"properties":{"noteIndex":0},"schema":""}(7)19EFW (g) = 5381.193 + 150.324*HC + 2.069*FL3 + 0.0232*AC3 - 6235.478[log1HC]Schild, 2004<1600g ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/uog.1741","ISSN":"09607692","author":[{"dropping-particle":"","family":"Schild","given":"R. L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fell","given":"K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fimmers","given":"R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gembruch","given":"U.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hansmann","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultrasound in Obstetrics and Gynecology","id":"ITEM-1","issue":"7","issued":{"date-parts":[["2004","12","1"]]},"page":"775-780","publisher":"John Wiley & Sons, Ltd","title":"A new formula for calculating weight in the fetus of ≤ 1600 g","type":"article-journal","volume":"24"},"uris":[""]}],"mendeley":{"formattedCitation":"(8)","plainTextFormattedCitation":"(8)","previouslyFormattedCitation":"(9)"},"properties":{"noteIndex":0},"schema":""}(8)BPD, AC, FL20EFW (g) = -5498.336 + 2101.261*ln(AC) + 15.613*FL2 +0.0577*BPD3Siemer, 2009 (<2500g) ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1055/s-2007-963645","ISSN":"0172-4614","PMID":"19137495","abstract":"PURPOSE Birth weight is an important predictive parameter for neonatal morbidity and mortality in the small fetus. Accurate estimation of fetal weight is therefore a valuable tool for determining the further obstetric management. The majority of studies presenting new formulas have included relatively small samples with a narrow range of birth weights, mostly term fetuses. In a previous study, we evaluated several weight formulas over the whole range of birth weights and in defined subgroups. We were able to show that some regression formulas appeared to be favorable within these subgroups. Notably, the highest levels of inaccuracy were found in the group of infants with a birth weight of less than 2500 g. This led us to hypothesize that a formula based on the lower birth weight group might increase the accuracy of weight estimation. The aim of the present study was therefore to develop a new specific formula for estimating weight in fetuses less than or equal to 2500 g and to compare the new regression formula with commonly used weight equations. MATERIALS AND METHODS This study included 260 pregnancies. The inclusion criteria were a singleton pregnancy; birth weight equal to or less than 2500 g; an ultrasound examination with complete biometric parameters within 7 days prior to delivery; and an absence of structural or chromosomal malformations. The data for the first 130 newborns were used to develop a new formula. The remaining 130 infants were used to evaluate the new regression formula and to compare it to commonly used weight equations. Stepwise regression analysis was carried out with the birth weight as the dependent variable and biometric parameters as independent parameters to obtain the best-fit formula. RESULTS The mean absolute percentage error for the new formula was 7.71 %. Compared to the other formulas, it generated the highest intraclass correlation coefficient. By the limits of agreement, the new formula demonstrated only a slight tendency towards underestimating fetal weight, and it provided the smallest range of all weight equations. CONCLUSION With proper application, our new formula can improve the accuracy of fetal weight estimation.","author":[{"dropping-particle":"","family":"Siemer","given":"J","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hilbert","given":"A","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hart","given":"N","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Meurer","given":"B","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Goecke","given":"T","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Schild","given":"R","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Ultraschall in der Medizin - European Journal of Ultrasound","id":"ITEM-1","issue":"01","issued":{"date-parts":[["2009","1","9"]]},"page":"47-51","title":"A New Sonographic Weight Formula for Fetuses?≤?2500 g","type":"article-journal","volume":"30"},"uris":[""]}],"mendeley":{"formattedCitation":"(9)","plainTextFormattedCitation":"(9)","previouslyFormattedCitation":"(10)"},"properties":{"noteIndex":0},"schema":""}(9)BPD, AC21EFW (g) = 9.337*BPD*AC - 229Thurnau, 1983 (<2500g) ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0002-9378(83)91195-X","ISSN":"0002-9378","abstract":"Based on ultrasonographic mensuration, a number of equations have previously been devised for the purpose of estimating fetal weights. The objective of this study was to develop a mathematical equation that is simple, accurate, and easy to use when applied to preterm or low-birth weight fetuses (<2,500 gm). Real-time ultrasound measurements of fetal biparietal diameters (BPDs) and abdominal circumferences (ACs) were obtained in 62 pregnant women within one week of premature delivery. Mean gestational age and mean birth weight ± SD for this study group of neonates were 28.5 ± 3.5 weeks and 1,135 ± 343 gm, respectively. With the aid of computer analysis, a simple regression equation was derived: EFW = (BPD x AC x 9.337) ?299. When predicted estimated fetal weight (EFW) was compared with actual birth weight (ABW), multiple regression analysis demonstrated a correlation coefficient (R) of 0.957. Preliminary results on 19 oatients of a prospective study showed an absolute mean difference between the computed EFWs and the ABWs to be within 7.0% of ABW (70 gm/kg of ABW). The standard deviation of the difference was 9.3% of ABW (93 gm/kg of ABW). Based on these data, this simple equation appears to be clinically reliable and easy to use when estimating weights of preterm or low-birth weight fetuses of less than 2,500 gm.","author":[{"dropping-particle":"","family":"Thurnau","given":"Gary R.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Tamura","given":"Ralph K.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sabbagha","given":"Rudy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Depp","given":"O.Richard","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Dyer","given":"Alan","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Larkin","given":"Ron","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Lee","given":"Timothy","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Laughlin","given":"Colby","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"American Journal of Obstetrics and Gynecology","id":"ITEM-1","issue":"5","issued":{"date-parts":[["1983","3","1"]]},"page":"557-561","publisher":"Mosby","title":"A simple estimated fetal weight equation based on real-time ultrasound measurements of fetuses less than thirty-four weeks' gestation","type":"article-journal","volume":"145"},"uris":[""]}],"mendeley":{"formattedCitation":"(10)","plainTextFormattedCitation":"(10)","previouslyFormattedCitation":"(11)"},"properties":{"noteIndex":0},"schema":""}(10)Table SEQ Table \* ARABIC 2: Maternal characteristics and pregnancy outcome of overall eFGR cohort and cases selected for inclusion in analysis. Where appropriate, statistical significance between the two groups is quoted.Entire eFGR cohort(n = 159)Cohort selected for final analysis(n = 65)SignificanceMaternal age (years)*30.8 + 5.931.8 + 5.97P = 0.26Maternal BMI (kg/m2)*27.6 + 6.2828.3 + 5.93P = 0.50Ethnicity+White BlackAsianOther74 (48%)18 (12%)29 (18%)35 (22%)31 (47.7%)4 (6.15%)15 (23.1%)15 (23.1%)P = 0.61Parity+PrimiparousMultiparous 93 (58%)66 (42%)32 (49.2%)33 (50.8%)P = 0.21Gestational age at delivery (weeks)*29.0 + 2.328.8 + 2.1P = 0.57Birthweight (g)^660 (210 – 1498)717 (350 – 1457)P = 0.87Sex+MaleFemale89 (56.0%)70 (44.0%)36 (55.4%)29 (44.6%)P = 0.94Pregnancy outcome+Live birth, still aliveStillbirthNeonatal death95 (59.8%)41 (25.8%)23 (14.5%)50 (76.9%)5 (7.7%)10 (15.4%)**P < 0.01Study population specific dataGestational age at scan (weeks)*28.6 + 2.1Estimated fetal weight at scan (g) ^ (using Hadlock BPD-HC-AC-FL)722 (357 – 1486)Amniotic fluid index (cm)* (n = 53)8.5 + 4.1Fetal presentation at scan+BreechCephalicTransverseNot recorded25 (38.5%)28 (43.1%)2 (3.1%)10 (15.3%)*mean + SD/t-test quoted for parametric data; ^median (range)/Mann-Whitney quoted for non-parametric data; + counts (percentage of total) Chi-squared quoted for categorical dataTable SEQ Table \* ARABIC 3: Top 3 performing models overall, and when the cohort is split by gestational age, EFW and fetal presentation. Number in brackets denotes distance to origin, which is calculated as a composite score to include both systematic and random errors, with a perfect model with a random error of 0% and a systematic error of 0% having a distance to the origin of 0. Mann Whitney used to determine if distance to origin differs within each category in the split cohort.Rank 1Rank 2Rank 3SignificanceOverallModel 2 (9.8)Model 1 (10.0)Model 5 (10.6)Gestational age < 28 weeksModel 2 (11.2)Model 1 (11.5)Model 5 (12.1)NSP = 0.62Gestational age > 28 weeksModel 2 (9.2)Model 1 (9.4)Model 5 (9.9)EFW < 750gModel 2 (10.8)Model 1 (11.0)Model 5 (11.6)NSP = 0.30EFW > 750gModel 19 (8.1)Model 2 (8.7)Model 1 (8.8)Fetal presentation: cephalicModel 2 (10.7)Model 1 (10.9)Model 5 (11.4)NSP = 0.52Fetal presentation: breechModel 2 (8.5)Model 1 (8.6)Model 5 (9.0)Symmetrical FGR (HC:AC < 95th centile)Model 2 (9.4)Model 1 (9.5)Model 9 (10.0)NS P = 0.62Asymmetrical FGR (HC:AC > 95th centile)Model 2 (10.3)Model 1 (10.6)Model 5 (11.0)Table SEQ Table \* ARABIC 4: Proportion of measurements within 5/10/15% of birthweight for top five performing models. ModelWithin 5%Within 10%Within 15%Above 15%241.564.686.213.8141.560.083.116.9536.956.981.518.5936.946.176.923.11936.949.278.521.5Table SEQ Table \* ARABIC 5: Correlation coefficients for each individual biometry parameter and the EFW (Pearson's method). ACHCFLEFWAC0.800.780.91HC0.800.680.84FL0.780.680.82EFW0.910.840.82SUPPORTING INFORMATIONTable S SEQ Supplementary_Table \* ARABIC 1: Systematic error + random error for each model, for overall cohort, and cohort split by gestation, EFW and fetal presentationModel numberOveralln = 65Gestational age (weeks)EFWPresentationSymmetric/asymmetric FGR<28/40n = 22>28/40n = 43<750gn = 37>750gn = 28Cephalicn = 25Breechn = 28HC:AC ratio <95th centile n = 31HC:AC ratio > 95th centilen = 3410.9 + 10.00.9 + 11.50.9 + 9.30.5 + 11.01.4 + 8.71.8 + 10.70.3 + 8.62.7 + 9.2-0.7 + 10.621.5 + 9.71.2 + 11.11.6 + 9.11.1 + 10.72.0 + 8.52.4 + 10.40.8 + 8.43.1 + 8.8-0.02 + 10.3333.3 + 23.847.2 + 22.426.3 + 21.547.0 + 20.815.2 + 13.133.0 + 24.231.3 + 23.830.0 + 27.236.4 + 20.3422.0 + 11.519.0 + 11.523.5 + 11.322.2 + 13.021.7 + 9.323.1 + 11.820.1 + 10.718.2 + 9.925.3 + 11.951.1 + 10.51.1 + 12.01.0 + 9.80.7 + 11.61.5 + 9.21.9 + 11.20.4 + 9.03.0 + 9.8-0.8 + 11.0610.8 + 13.28.1 + 13.612.2 + 12.910.4 + 14.511.4 + 11.510.7 + 14.310.0 + 12.29.4 + 12.812.1 + 13.6723.4 + 16.919.0 + 16.325.7 + 16.922.8 + 18.224.2 + 15.324.0 + 18.821.4 + 14.618.5 + 15.727.9 + 16.9813.8 + 14.910.3 + 14.615.7 + 14.913.5 + 16.214.2 + 13.314.2 + 16.412.2 + 13.110.0 + 14.017.2 + 15.09-0.7 + 10.90.2 + 12.1-1.1 + 10.4-1.1 + 11.6-0.01 + 10.00.2 + 12.2-0.9 + 9.03.4 + 9.4-4.3 + 11.01024.1 + 14.924.2 + 15.024.1 + 15.123.2 + 15.025.4 + 15.024.0 + 16.524.6 + 15.131.1 + 17.017.8 + 13.21111.9 + 12.312.1 + 13.211.8 + 12.011.4 + 13.212.6 + 11.211.8 + 13.812.4 + 11.817.0 + 11.07.3 + 11.8129.3 + 12.412.6 + 13.47.5 + 11.613.3 + 13.33.9 + 8.88.9 + 12.28.7 + 13.39.4 + 12.99.1 + 12.1138.5 + 13.77.4 + 14.59.0 + 13.57.2 + 14.810.2 + 12.27.7 + 14.89.6 + 14.614.0 + 11.93.5 + 13.514-9.4 + 11.6-10.5 + 12.2-8.9 + 11.4-10.7 + 12.5-7.8 + 10.2-10.1 + 12.5-8.5 + 12.3-4.8 + 10.0-13.7 + 11.415-1.1 + 13.3-3.3 + 13.40.04 + 13.2-3.5 + 13.82.1 + 12.1-1.8 + 14.30.05 + 14.14.6 + 11.6-6.3 + 12.7168.3 + 13.38.3 + 14.28.3 + 12.97.9 + 14.48.8 + 11.87.5 + 14.29.3 + 14.113.5 + 11.63.6 + 13.1 17-44.1 + 11.1-36.8 + 10.1-47.8 + 9.7-37.9 + 9.6-52.2 + 6.8-43.9 + 12.0-44.7 + 10.2-44.8 + 11.8-43.5 + 10.5188.1 + 10.68.9 + 12.17.7 + 9.89.0 + 11.77.0 + 9.09.2 + 11.17.1 + 9.28.7 + 9.47.6 + 11.6194.9 + 10.46.3 + 11.54.1 + 9.97.2 + 11.51.7 + 7.95.6 + 10.33.5 + 10.32.9 + 10.16.7 + 10.52049.5 + 16.750.9 + 19.648.8 + 15.550.7 + 18.847.8 + 14.149.5 + 18.249.5 + 15.653.2 + 16.946.1 + 16.42134.9 + 17.235.8 + 16.834.4 + 17.638.9 + 18.129.6 + 14.634.6 + 18.633.4 + 15.231.0 + 17.338.4 + 16.6 ................
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