Delayed descent of the fetus anteriorly

Definition. Slow descent is an abnormally slow rate of descent of the presenting part of the fetus. The definition of this condition varies depending on the number of births a woman has had - in primiparous women, the presence of such an anomaly is indicated by a maximum slope on the descent curve of the presenting part of the fetus equal to 1 cm/h or less; the presence of this pathology in a woman with repeated births can be said if the maximum slope on the descent curve is equal to 2 cm/h or less.

Diagnosis. As with prolonged active dilation, the diagnosis of delayed descent requires determining the tendency to descent. This can be calculated based on two vaginal examinations performed at an interval of 1 hour, but the accuracy of the diagnosis increases if the observation period lasts 2 hours and includes at least three vaginal examinations.

The normal tendency of descent of the presenting part of the fetus for primiparous women is 3.3 cm/h; the 5th percentile value is 0.96 cm/h. For multiparous women it is 6.6 cm/h; the 5th percentile value is 2.1 cm/h. Values below 1 cm/h for primiparous women and less than 2 cm/h for women with repeated births are abnormal.

Frequency: Delayed descent of the presenting part of the fetus is observed in 4.7% of births.

Causes. The discrepancy between the sizes of the fetus and the mother's pelvis, overdose of tranquilizers, regional anesthesia and abnormal presentation of the fetus are such frequent factors in delayed descent that they should be assigned an etiologic role. In this type of labor anomaly, the discrepancy in size occurs in 26.1% of primiparous women and in 9.9% of women with repeated births.

Diagnostics. Similar to the stop of descent, slow progression of the presenting part of the fetus is observed when it is large (body weight over 4000 g).

Mild types of abnormal fetal presentation (occiput turned backwards, transverse position of the head, asynclitism), which in most cases do not play a significant role with normal fetal size, become important causal factors in the development of labor anomalies with a large fetus. Abnormal fetal presentation with its large size is often of fundamental importance in natural birth canal or cesarean section.

Due to the widespread use of epidural anesthesia in recent years, it has become an important etiologic factor in motor activity disorders associated with the descent of the presenting part of the fetus, and affects the ability of the woman in labor to push in the second stage of labor. Women with epidural anesthesia used during labor are much more likely to experience disorders in the descent of the presenting part of the fetus - they more often have a cesarean section and the application of obstetric forceps.

In women who have given birth to many children, a common etiological factor for delayed descent of the fetus is the insufficiency of the uterine expelling forces in the second stage of labor.

With good contractions during the active phase, they sometimes experience a decrease in uterine activity with full dilation of the cervix and a relatively high position of the presenting part of the fetus (from -1 to +1), which can be determined based on clinical signs (contractions become significantly less frequent and shorter) using an intrauterine catheter. This simple problem can be eliminated by gentle stimulation with oxytocin.

Prognosis. The prognosis of labor with a slow descent of the presenting part of the fetus largely depends on the possible subsequent complete cessation of fetal progression through the birth canal. Women in labor who experience constant descent of the presenting part of the fetus have a good prognosis for uncomplicated vaginal delivery (approximately 65% of cases). In 25% of them, the use of obstetric forceps is necessary. If the slow descent of the presenting part of the fetus is further complicated by its cessation, the prognosis becomes unfavorable: in 43% of cases it ends in a cesarean section, in 18% - in labor using obstetric forceps. In addition, in women with slow passage of the fetus through the birth canal, who were stimulated with oxytocin or obstetric forceps were used, perinatal mortality reaches 69%, the frequency of low assessment on the Apgar scale is 32%.

Management of labor with slow descent of the presenting part of the fetus

The primary management objective is to rule out obvious causes of complications such as epidural anesthesia, overdose of sedatives, abnormal presentation of the fetus, and large fetal size.

In the absence of these factors, one should suspect the presence of a discrepancy between the sizes of the fetus and the mother's pelvis, especially in primiparous women, which is observed in approximately 30% of cases. To resolve this issue, it is necessary to determine the pelvic dimensions using clinical methods (the Gillis-Muller maneuver). If a discrepancy is detected, pelvimetry should be performed. X-ray assessment of the pelvic and fetal dimensions is also required in cases where the delay in descent turns into a complete stop, which is observed in most women in labor with slow descent and large fetuses. Treatment should be aimed at eliminating the established etiologic factor. In case of epidural anesthesia or overdose of sedatives, expectant tactics are used until the effect of these factors decreases. In case of a discrepancy between the sizes of the fetus and the mother's pelvis, delivery by cesarean section is required, with weak contractions - stimulation with oxytocin.

Caesarean section is also the method of choice for women in labor with abnormal presentation of a large fetus.

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