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MINISTRY OF PUBLIC HEALTH OF UKRAINE
National Pirogov Memorial Medical University, Vinnytsya
CHAIR OF OBSTETRICS and Gynecology №1
Methodological instruction for practical class for foreign students
Uterine birth activity anomalies
Module 2: Obstetrics and gynecology
Context module 9: Pathology of pregnancy, labor and puerperium
Aim: to learn the causes, clinic, diagnostic, treatment and preventing measures of abnormalities of uterine contractions.
Basic level:
1. Estimation of normal uterine contractions.
2. Medicines which are used for normalization of uterine contractions
STUDENTS' INDEPENDENT STUDY PROGRAM
I. Objectives for Students' Independent Studies
You should prepare for the practical class using the existing textbooks and lectures. Special attention should be paid to the following:
1. Obstetrics terminology.
2. External and internal obstetric examination.
3. Segments of fetal head
4. Lower segment of uterine and contraction ring.
5. Signs of normal uterine contractions
6. Conduct of normal labor & delivery and their clinic.
7. Classification of uterine contractions abnormalities.
8. Factors that provide normal uterine contractions.
9. Definition of primary and secondary uterine inertia.
10. Incoordinative uterine activity,
11. Excessive uterine activity.
12. Medicines for correction of uterine contractions.
13. Methods of treatment of uterine inertia in the first and second stages of labor.
14. Prevention of uterine contractions abnormalities.
Key words and phrases: uterine dysfunction, hypotonic and hypertonic, incoordinative, excessive uterine activity.
UTERINE BIRTH ACTIVITY ANOMALIES
Birth activity anomaly is the state when frequency, duration, rhythm and force of parodynia and labor do not provide dynamic, within the physiological parameters of time, advancement of the fetus and its expulsion without delivery biomechanism violation.
Disorders of any index of uterine activity are possible — uterine tone, rhythm, frequency and coordination of contractions, intervals between labor pains, delivery duration.
Correct diagnosis and management of abnormal labor requires evaluation of the mechanisms of labor: in classic terms, the "power," the "passanger,"an the "passage," otherwise refferred to as the uterine contractions, fetal factors (e.g., presentation, size), and the maternal pelvis, respectively: power, or strength, duration and frequency of uterine contractions, evaluated both qualitatively and quantitatively. Frequency and duration of contractions can be subjectively evaluated by manual palpation of the maternal abdomen during contraction. Strength of uterine contractions is often judged by how much the uterine wall can be "indented" by an examiner's finger during a contraction: strong contraction no indetation; moderate contraction, some indentation; mild contraction, considerable indentation. Although subjective, such determinations by experienced examiner are of value. The frequency and duration of uterine tractions may be measured more accurately by using a tocodynamometer while performing external electronic fetal monitoring.
For cervical dilatation to occur, each contraction must generate at least 25 mm Hg of pressure, with 50 to 60 mm Hg being considered the optimal intrauterine pressure. The frequency of contractions is also important in generating a normal labor pattern; a minimum of three contractions in a 10- minute widow is usually considered adequuate.
During the first stage of labor, arrest of labor should not be diagnosed until the cervix is at least 4 cm dilated ( i.e., the latent phase of labor has been completed) and a pattern of uterine contractions that is adequate both in frequency and intensity has been established.
The early part, or latent phase, of labor is involved with softening and effacement of the cervix with minimal dilatation. This is followed by a more rapid rate of cervical dilatation, known as the active phase of labor, which is further divided into acceleration and deceleration phases.
The descent of the fetal presenting part usually begins during the active phase of labor, than progresses at more rapid rate toward after the cervix is completely dilated. A useful method for assessing the progress of labor and detecting abnormalities in a timely manner is to plot the rate of cervical dilatation and descent of the fetal presenting part.
Normal cervical dilatation and descent of the fetus take place in a progressive manner and occur within a well-defined time period. Dysfunctional labor occurs when rates of dilatation and descent exceed these time limits.
The normal limits of the latent phase of labor extend up to 20 hours for nulliparous patients and up to 14 hours for multiparous patients. A latent phase that exceeds these limits is considered prolonged and may be caused by hypertonic uterine contractions, premature or excessive use of sedatives or analgesics, or hypotonic. uterine contractions.
Hypertonic contractions are ineffective, painful and are associated with increased uterine tone, whereas hypotonic contractions are usually less painful and are characterized by an easily indictable uterus during the contractions.
Hypotonic contractions occur more frequently during the active phase of labor. A long, closed, firm cervix requires more time to efface and to undergo early dilatation than does a soft, partially effaced cervix, but it is doubtful that a cervical factor alone causes a prolonged latent phase. Some patients who appear to be developing a prolonged latent phase are shown eventually to be in false labor, with no progressive dilatation of the cervix.
Palpation or recording of uterine contractions and observation of the patient over a period of time usually suggests whether uterine activity is hypotonic or hypertonic or whether the patient is in false labor.
The management of a prolonged latent phase depends on its cause. A prolonged latent phase caused by premature or excessive use of sedation or analgesia usually resolves spontaneously after the effects of the medication have disappeared. Hypertonic activity responds erratically to oxytocin but usually responds to a therapeutic rest with morphine sulfate or an equivalent drug.
Hypo contractile dysfunction usually responds well to an intravenous oxytocin infusion.
When the cervix dilates to approximately 3 to 4 cm, the rate of dilatation progresses more rapidly. Cervical dilatation of less than 1.2 cm/hour in nulliparous women constitutes a protraction disorder of the active phase of labor. During the latter part of the of the active phase, the fetal presenting part also descends more rapidly through the pelvis and continues to descend | through the second stage of labor. A rate of descent of presenting part of less than l.0 cm/hour in nulliparous women and 2.0cm/hour in multiparous women is considered to be a protraction disorder of descent.
During the second stage of labor, the "powers" include both the uterine contractile forces and voluntary maternal expulsive efforts (pushing). Maternal exhaustion, excessive anesthesia, or other conditions such as cardiac disease or neuromuscular disease may already affect these combined forces so that they are insufficient to result in vaginal delivery or cesarean section may then be required.
In the absence of cephalopelvic disproportion or fetal malposition, protraction or arrest disorders are usually caused by hypotonic uterine; contractions, conductions anesthesia, or excessive sedation.
A prolonged latent phase can be managed by either rest or augmentation of labor with intravenous oxytocin once mechanical factors have been ruled out. If the patient is allowed to rest, one of the following will occur; she will cease having contractions, in which case she is not in labor; she will go into active labor; or she will continue as before, in which case oxytocin may be administered to augment the uterine contractions. The use of arnniotomy, or artificial rupture of membranes, is also advocated [or patients with prolonged latent phase.
During the active phase of labor, mechanical factors such as fetal malposition and malpresentation as well as fetopelvic disproportion must be considered before augmentation of uterine contractions with oxytocin. In cases in which the fetus fails to descend in case of adequate contractions, disproportion is likely and cesarean section warranted. If no disproportion is present, oxytocin can be used if uterine contractions are judged to be inadequate. In cases of maternal exhaustion resulting in secondary arrest of dilatation, rest followed by augmentation with oxytocin is often effective.
Classification of birth activity anomalies:
I. Pathological preliminary period (false labor).
II Powerless labor (hypoactivity or inertness of the uterus):
primary;
secondary;
parodynia weakness: a) primary; b) secondary.
Excessively strong birth activity (uterine hyperactivity).
Discoordinated birth activity:
discoordination;
hypertone of the inferior uterine segment (reverse gradient, inversion);
uterine tetanus (spasmodic labor pains);
circular dystocia (contraction ring).
1. PATHOLOGICAL PRELIMINARY PERIOD
The preliminary period is observed in 33 % pregnant women at the term of pregnancy of 38—40 weeks. The normal preliminary period is characterised by infrequent, weak spasmodic pain in the underbelly and loin, which appears against the background of normal uterine tone. Its duration may reach 6—8 h. Mature neck of uterus is diagnosed in 87 % women.
The pathological preliminary period is characterised by painful, intermittent by force and sensation dilating pains, which arise against the background of increased uterine tone. The pains are similar to labor pains, but do not lead to structural changes and cervical dilatation. The pains stimulate the pregnant woman, lead to the violation.
of the diurnal sleep rhythm and total activity. The duration of pathological preliminary period makes more than 8—12 h.
The pathological preliminary period is observed in women with functional changes of central nervous system regulation (fear of labor, neurosis), neurocirculatory dystonia, endocrine system malfunction, vegetative disorders. The pathological preliminary period may directly turn into uterine inertia.
Treatment:
sedatives and debilitants (diazepam, promedol);
if it is ineffective — single-stage application of tocolytic therapy with beta-adrenoceptor agonists (hexoprenalin 25 mg (5 ml) diluted in 500 ml of sodium chloride isotonic solution and introduced i.v. drop-by-drop slowly 10—15 drops per min);
preparation to delivery by intravaginal introduction of prostaglandin E2.
Contraindications to beta-adrenoceptor agonists application:
hypersensitivity;
premature placenta detachment;
uterine hemorrhage;
endometritis;
extragenital pathology at decompensation stage;
— myocarditis;
hyperthyroidism;
glaucoma.
Side effects of beta-adrenoceptor agonists: headache; vertigo; tremor; tachycardia; ventricular extrasystole; heart pains, ABP reduction.
If tachycardia arises (>100 bprn), introduction of verapamil and potassium preparations is administered to the parturient woman.
2. POWERLESS LABOR (WEAK UTERINE CONTRACTIONS)
Powerless labor (PL) is a condition with insufficient intensity, duration and frequency of labor pains, therefore smoothing, dilation of the uterine neck and fetus advancement at its correspondence with pelvic dimensions are decelerated.
There are differentiated primary and secondary types of PL. Primary PL arises at the very beginning of delivery and lasts during the period of dilation. PL arising after a period of long-term regular birth activity and manifesting itself with typical signs indicated above is called secondary.
PL may be diagnosed during 4—6 h of clinical observation and during 2 h if hystcrography is possible.
Excessively intensive birth activity develops unexpectedly. Strong labor pains take place in a short interval of time, uterine contractions frequency is more than 5 in 10 min, which promotes quick and sufficient dilation of the uterine orifice.
Parturition is considered rapid if it lasts less than 6 h in pri-mipara women and 4 h in secundipara women, and accelerated — less than 4 and 2 h accordingly. Such types of delivery cause injuries of the uterus and fetus (deep ruptures of the uterus, vagina, perineum, premature detachment of normally located placenta, hypotonic bleeding, cord rupture, cerebral hemorrhage, cephalohcmato-mas).
Treatment:
Oxytocin (deaminooxytocin or sandost, sandopard 25—50 IU, in. the active phase only) or preparation containing oxytocin (pituit-rin, hyphotocin, mammophysin).
Prostaglandin E2 (dinoproston, prostin E2, prostarmon E, menzaprost-1) 0.5 mg — pills, 5 ml — ampoules (before 4 cm cervical dilation).
P-adrenoceptor blocking agents (obsidan, propranolol) 5 mg/400 ml of physiological solution.
Aprophen (1 % — 1 ml) — peripheral and central M- and 11-anticholinergic drug — relaxes the neck of uterus, intensifies uterine contractions.
Ozonized transfusion media.
Cesarean section if uterine inertia is combined with fetal hypoxia.
3. DISCOORDINATED BIRTH ACTIVITY
The frequency of discoordinated birth activity (DBA) makes 1-3%. There are no coordinated contractions in different uterine parts (right and left, superior and inferior parts, violation between uterine parts up to fibrillation and tetanus). It usually develops at the 1st stage of delivery till the uterine neck dilates to 5— 6 cm.
The clinical picture is characterised by the hypertone of the inferior segment, irregular, strong, sharply painful parodynia that reminds the picture of threatening hysterorrhexis.
Clinical signs:
pain;
violated rhythm of labor pains;
no dynamics of cervical dilation;
no head advancement;
hypertone of the inferior uterine segment (reverse gradient);
spasmodic parodynia (uterine tetany);
dystonia of the neck of uterus.
The character of birth activity is detected on the basis of quantitative assessment of the three main processes:
dynamics of uterine contractions;
dynamics of cervical dilation;
dynamics of the advancement of the presenting part of the fetus along the parturient canal.
Assessment methods:
1.Uterine activity assessment:
subjective sensation of the parturient woman (inaccurate, different threshold of pain sensitivity);
palpation;
external cardiotocography (single-channel and multichannel);
internal tocography.
The cervix of uterus: vaginal examination; ecrvieodilatometry.
Descending part: vaginal examination; perineal US.
Treatment. Delivery stimulation therapy with oxytocin, prostaglandins and other uterotonics at DBA is absolutely contraindicated, otherwise uterine tetanus is possible.
The basic components of DBA treatment.
Anticholinergic drugs.
Anesthetics (tramal, tramadol, promedol, preparations of morphine type).
beta-adrenoceptor agonists (partusisten, intrapartal).
Psycotherapy, electroanalgesia, seduxen, relanium, narcosis.
Peridural anesthesia.
Amniotomy.
Cesarean section.
Conditions of administration of uterotonics:
absence of fetal bladder;
correspondence of fetal dimensions to the maternal pelvis.
Contraindications:
clinically and anatomically contracted pelvis;
operated uterus;
anomalous positions and presentations of the fetus;
fetal distress;
complete placental, presentation;
premature detachment of the normally and low located placenta;
vaginal stricture;
renewed perineal rupture of the 3rd degree;
dystocia, atresia, scar changes of the neck of uterus;
hypersensitivity.
Treatment:
terbutaline in the dose of 250 meg i.v. slowly during 5 min or salbutamol — 10 mg in 1 L of physiologocal liquids for i.v. infusions or Ringer's lactate — 10 drops a min.
Criteria of birth activity character assessment:
A. Tocographically (Table 1):
Table 1. Tocographic Criteria of Birth Activity Assessment
| |Hypo- |Norm |Hyperdynamics |
| |dynamics | | |
|Labor pains frequency per 10 min | 5 |
|Basal tone, mm of mercury |12 |
|Labor pains intensity (amplitude), mm Hg | 50 |
|Labor pains duration, sec | 100 |
|Irregular rhythm, min |3 |1-2 | |7.5 h (5) |< |
|(Smoothing of the uterine cervix, the rate of dilation up to 3—4 cm) | |0.35 cm/h | |
|Active phase (duration) |> |2-3 h (1-1.5) |< |
|(The rate of dilation from 4 to 8 cm) | |1.5 cm/h | |
|Deceleration phase (duration) |> |1.5-2 h (1-1.5) |< |
|(The rate of dilation from 8 to 10 cm) | |1.0 cm/h) (1.5) | |
|Duration of the 1ststage |> 18(14) |10-12 h (6-7) | ................
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