Secondary arrest of cervical dilation

Secondary arrest of cervical dilation can be recorded when, during the period of maximum rise on the Friedman curve in the active phase of labor, dilation stops for 2 hours or more.

Diagnostics

The diagnosis of secondary arrest of cervical dilation requires at least two vaginal examinations, 2 hours apart, confirming the absence of dilation during this period. The arrest must be recorded during the maximal ascent phase of the cervical dilation curve, to avoid confusion with a prolonged latent phase (an abnormality that occurs when the maximal ascent phase has not yet begun) or a prolonged retardation (an abnormality that occurs when the maximal ascent phase has ended).

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Frequency

The most common abnormality observed during the active phase of labor is secondary arrest of cervical dilation, which is observed in 6.8% of primiparous women and 3.5% of multiparous women. According to E. Friedman et al. (1978), it is observed somewhat more frequently - 11.7% for primiparous women and 4.8% for multiparous women. In any case, this abnormality of labor is more common in primiparous women and is often a component of situations where several abnormalities of labor are observed simultaneously.

Reasons

In secondary cervical dilation arrest, the etiologic factor is the discrepancy between the sizes of the fetus and the mother's pelvis in approximately 50% of cases. Such a high frequency of discrepancy requires a strict assessment of the ratio of the sizes of the fetus and the mother's pelvis in each case when this anomaly of labor is detected. Another etiologic factor is the incorrect position of the fetal head, as well as excessive anesthesia and regional anesthesia. Quite often, a combination of two or more of these factors is observed, including discrepancy.

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Forecast

The high frequency of fetal-pelvic size discrepancy in women in labor with secondary cervical dilation arrest forces us to speak cautiously about the prognosis of these conditions. Using pelvimetry, it is possible to determine the presence of absolute size discrepancy in 25-30% of women with this anomaly of labor. After a fairly active attempt to normalize the course of the latter, it turns out that another 10-15% of women in labor (most of whom have a borderline discrepancy between the fetal and maternal pelvic sizes) do not experience the effect of treatment and they require the end of labor by cesarean section. The rest of the women in labor (approximately 55%) end labor through the natural birth canal.

Labor management begins with determining the ratio of the sizes of the fetus and the mother's pelvis to confirm the presence of a discrepancy and to exclude unnecessary and potentially dangerous stimulation of labor.

The most important clinical technique used to assess the ratio of the fetus to the mother's pelvis (the existing methods for assessing the disproportion between the fetus and the mother's pelvis - roentgenopelviometry, echography, nuclear magnetic resonance, etc. - are not sensitive enough) is the test proposed by Gillis and Muller. To perform it, the obstetrician performs a vaginal examination before the contraction or at its very beginning. When the contraction reaches its peak, an attempt is made to push the presenting part of the fetus into the small pelvis by pressing with the free hand on the fundus of the uterus. At the same time, with the hand inserted into the vagina, an attempt is made to determine the possible descent of the presenting part of the fetus into the small pelvis of the woman in labor with a push-like pressure of the doctor's free hand on the abdominal wall in the area of the fundus of the uterus. If the presenting part moves very little or does not move at all, then the probability of a discrepancy between the sizes of the fetus and the mother's pelvis is very high. If the presenting part easily moves into the small pelvis, then the discrepancy is unlikely.

In women in labor with secondary arrest of labor and limited fetal mobility during the Gillies-Muller test, it is recommended to perform an assessment using X-ray pelvimetry, which makes it possible to diagnose an absolute discrepancy between the sizes of the fetus and the mother's pelvis and exclude further attempts at vaginal delivery in approximately 1/3 of women in labor with secondary arrest of cervical dilation. Another 1/3 of women in labor have borderline values, and 1/3 have no discrepancy in size. If clinical discrepancy is confirmed, it is necessary to perform delivery by cesarean section without further delay.

If the sizes of the pelvis and the fetal head correspond (positive Gillis-Muller test, pelvimetry), stimulation of labor is required using internal hysterography, direct fetal electrocardiography, and determination of the current pH from the fetal head. Most of these women in labor have decreased uterine activity, and reasonable use of oxytocin allows eliminating the disorders associated with the cessation of labor, as well as achieving a normal birth of the fetus.

Some women in labor with secondary cervical dilation arrest and normal or borderline pelvimetry results (both with the Gillis-Muller test and with X-ray examination) have fairly good labor activity (contractions every 2-2.5 minutes lasting 60 seconds; pressure at the height of contraction is more than 50 mm Hg). There are conflicting opinions on the management of such pregnant women.

Some obstetricians consider the uterine activity to be quite satisfactory in this pathology, and additional stimulation to be undesirable and even sometimes dangerous. According to others, the uterine activity is reduced because it does not lead to sufficient opening of the cervix; in the absence of disproportion between the sizes of the pelvis and the fetal head in these women in labor, successful careful (!) stimulation is possible in many cases, since the use of oxytocin in women in labor with sufficiently effective labor activity can be dangerous and should be carried out with extreme caution.

Treatment should be initiated with oxytocin 0.5 mIU/min, and if careful assessment reveals no signs of hyperstimulation or a threatening fetal condition, the dose can be increased periodically by 0.5 mIU/min at 20-minute intervals. In such cases, the maximum dose of 0.5 mIU/min should not be exceeded.

In this management of women in labor, the question arises - for how long and in what quantity should oxytocin be administered to increase the activity of labor. Almost all women in labor experience an effect within a 6-hour period of stimulation, although 85% have a positive reaction already in the first 3 hours. A positive reaction in response to stimulation is characterized by the appearance of an increase in the curve of cervical dilation. Therefore, a 3-hour period of normal uterine activity (after arrest) creates sufficient conditions for the restoration of labor in women in labor with secondary arrest of cervical dilation, receiving oxytocin treatment.

If after a 3-hour period of stimulation and more active labor there is no further dilation of the cervix, further attempts to achieve vaginal delivery are unjustified and the delivery should be completed by cesarean section.

With a good effect of oxytocin stimulation, the rise in the cervical dilation curve after the stoppage may be the same or even higher than before. In these cases, the prognosis is favorable and there are all possibilities for vaginal delivery.

If there is no response to oxytocin or the rise in the cervical dilation curve is less than before the arrest, the situation must be seriously re-evaluated, since in many such cases the discrepancy between the fetal and maternal pelvic dimensions was missed during the first assessment. The Gillies-Muller maneuver should be repeated and the radiographs and pelvimetry results should be carefully analyzed to determine the source of the error. As a rule, a disproportion between the fetal pelvis and head is usually detected and a cesarean section must be performed.

There are some differences in the nature and outcome of secondary arrest of cervical dilation depending on the time of its development in the process of labor. Indeed, early arrest is often associated with a discrepancy between the sizes of the fetus and the mother's pelvis and requires surgical intervention much more often than arrest that occurs in the active phase of labor. In addition, when there is a good response to oxytocin stimulation during early arrest, the rise in the cervical dilation curve after arrest is usually higher than that noted before it, and there is an excellent chance of vaginal delivery. In other words, early arrest is rarely amenable to correction, but those cases in which there is a good response to oxytocin have a favorable prognosis.

If the cervical dilation stops again, the delivery should be completed by cesarean section unless it is possible to establish the presence of factors other than incompatibility (epidural anesthesia, overdose of sedatives) that could have caused the stop again.

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