TESTING OPTIONS FOR CHROMOSOMAL ABNORMALITIES …
Chromosomal Abnormalities in Term, Live born Newborns
Maternal Age Risk of Abnormalities
20. 1/526
21. 1/526
22. 1/526
23. 1/500
24. 1/476
25. 1/476
26. 1/476
27. 1/455
28. 1/435
29. 1/417
30. 1/385
31. 1/385
32. 1/322
33. 1/286
34. 1/238
35. 1/192
36. 1/156
37. 1/127
38. 1/102
39. 1/83
40. 1/66
41. 1/53
42. 1/42
43. 1/33
44. 1/26
45. 1/21
46. 1/16
47. 1/13
48. 1/10
49. 1/8
TESTING OPTIONS FOR CHROMOSOMAL ABNORMALITIES AND BIRTH DEFECTS
WOMEN OB/GYN, P.A.
2003 Medical Parkway
Suite 250
Annapolis, MD 21401
(410)224-2228
Dr. Miriam Yudkoff
Dr. Janice Bird
Dr. Melissa Moen
Dr. Nicolle Bougas
Dr. Jackie Nichols
Introduction
Almost all children in the United States are born healthy. Out of 100 newborns, only two or three have major birth defects. A birth defect is a physical problem that is present at birth. It also is called a congenital disorder or malformation. For about 70% of babies born with birth defects, the cause is not known. In other cases, birth defects are inherited through genes or chromosomes.
Birth defects are caused by an error in the way the baby develops. A birth defect may affect how the body looks, works, or both. Many birth defects are mild, but some can be severe. Babies with birth defects may need surgery or medical treatment. Most birth defects occur during the first 3 months of pregnancy. Some can be found before birth with special tests. Others appear at birth or later in a person’s life.
A normal human has 23 pairs of chromosomes for a total count of 46 chromosomes. One set is from the mother and the other set is from the father. If a person has an extra or missing chromosome(s), this is called aneuploidy. Depending on the exact chromosome that is missing or extra, there may be birth defects, such as mental retardation, heart or intestinal defects, or fetal death before or after birth. The most common chromosomal abnormality is an extra chromosome known as “Down Syndrome.”
Prenatal Testing
Different types of tests are offered to all pregnant women early in pregnancy to assess their risk of having a baby with a birth defect or abnormal chromosomes. Tests offered include screening tests, diagnostic tests, and sonograms. A screening test is a noninvasive test such as blood test that will determine if you have an increased or decreased chance for your current pregnancy to be affected by aneuploidy. The risks to you or your fetus are minimal; however, screening tests can be associated with a false positive (an abnormal result when the fetus is normal) or a false negative (a normal result when the fetus is abnormal). A diagnostic test is an invasive test that can be associated with risks to the baby or you, but will tell with almost 100% accuracy if the fetus has abnormal chromosomes. A sonogram at 18-20 weeks may be able to detect structural abnormalities of fetal growth and development such as brain, heart, spine, gastrointestinal, and kidneys.
Screening Tests
First trimester:
Nuchal translucency + PAPP-A and HCG blood test
Between 11 weeks and 13 6/7 weeks
The nuchal translucency is a special sonogram measuring the amount of fluid below the skin in the fetal neck. This in combination with blood tests for PAPP-A and HCG has a detection rate for aneuploidy from an extra chromosome 21 (Down syndrome) or 18 (Edward syndrome) of 75% - 86%.
You would be eligible for this test_________________________
You must call the office to schedule this appointment at least 24 hours in advance.
Second Trimester:
Maternal Serum Screen 4 (MSS4) between 15 and 19 weeks
This blood test for 4 biochemical markers, (AFP, HCG, estriol, DIA), has a detection rate of 75% - 80% for aneuploidy. It will also detect 80% of open neural tube defects, which is incomplete closure of the fetal spine that can cause spina bifida or anencephaly.
Sequential Screening
Combines First and Second Trimester screening to increase the detection rate for aneuploidy to 90% - 92%, with a 3.5% false positive rate. If any screening test is positive an amniocentesis or sonogram is recommended to determine if there truly is a problem.
Diagnostic Tests
Chorionic Villus Sampling (CVS) at 10-12 weeks: A thin tube (catheter) is threaded usually through the vagina and cervix into the uterus and a small sample of the placental tissue is obtained. This tissue can be “grown” to determine the exact number of chromosomes of the fetus. It usually takes 2 – 3 weeks for the final results. There is a small chance of complications (0.5 – 1%) such as infection, miscarriage or failure of the cells to grow.
Amniocentesis at 15-19 weeks: In this test, a needle is passed through the abdomen into the uterus to collect some of the amniotic fluid surrounding the baby. Some of the fetal cells which are found in the fluid can be “grown” to determine the exact number of chromosomes of the fetus. It usually takes 2-3 weeks for the final results. This procedure has a small chance of complications, (0.3-1%), such as infection, ruptured membranes, miscarriage or failure of the cells to grow.
What Should I do?
In our experience, most women chose to proceed with screening tests. However, not all do. Most find a normal test reassuring. Consider what you would do with the test results if an abnormal fetus is found. Some would want the information to be “prepared.” Others may wish to terminate the pregnancy. Others may choose not to know. You must decide what is best for you. The providers of Women Ob/Gyn are here to answer any questions you have and to help you obtain any of the above testing options that are right for you. It is your responsibility to find out what tests your insurance company covers.
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