Delayed lowering of the presenting part of the fetus

Definition. Delayed lowering is a pathologically slow rate of lowering the presenting part of the fetus. The definition of this condition varies depending on the number of births in a woman, in primiparous women the presence of such anomaly is indicated by the maximum slope on the curve of the lowering 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 in the event that the maximum slope on the descent curve is equal to 2 cm / h or less.

Diagnostics. As with the protracted active phase of cervical dilatation, it is necessary to determine the tendency to lowering in order to diagnose a delayed descent. It can be calculated from the data of two vaginal examinations conducted 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 lowering the presenting part of the fetus for primiparum is 3.3 cm / h; the values of the 5th percentile are 0.96 cm / h. In the case of multi-breeders, it is 6.6 cm / h; the value of the 5th percentile is 2.1 cm / h. The figures below 1 cm / h for primiparas and less than 2 cm / h for women with repeated births are a deviation from the norm.

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

Causes. The discrepancy between the size of the fetus and the pelvis of the mother, an overdose of tranquilizers, regional anesthesia and false presentation of the fetus are so frequent factors with a slow descent that they should be given an etiological role. In this type of anomaly of labor activity, a discrepancy in size occurs in 26.1% of the primiparous and in 9.9% of women with repeated births.

Diagnostics. Similarly to stopping the lowering, the slow progression of the presenting part of the fetus is observed at its large sizes (body weight more than 4000 g).

The non-severe types of miscarriage of the fetus (occiput is reversed, the transverse position of the head, asynclitism), which in most cases do not play a significant role at its normal size, become important causative factors in the development of abnormalities of labor in a large fetus. Misalignment of the fetus with its large size is often of fundamental importance at delivery through natural birth canal or by caesarean section.

In view of the widespread use of epidural anesthesia in recent years, it has become an important etiologic factor in motor disorders associated with the lowering of the fetus, affecting the maternity's ability to push in the second stage of labor. In women with epidural anesthesia applied during labor, infrequent lowering of the presenting part of the fetus is much more common: they often produce a cesarean section and the imposition of obstetric forceps.

In multiparous women, the widespread etiologic factor of delayed lowering of the fetus is the inadequacy of the expelling forces of the uterus in the second stage of labor.

With good battles during the active phase, they sometimes have a decrease in uterine activity with full neck opening and relatively high standing of the fetus (from -1 to +1), which can be determined on the basis of clinical signs (fights become much rarer and shorter) using an intrauterine catheter. This uncomplicated problem can be eliminated by careful stimulation with oxytocin.

Forecast. The prognosis of labor with the delayed lowering of the presenting part of the fetus depends to a large extent on the possible onset of a complete stop of fetal progression through the birth canal. The parturient women who have a constant lowering of the presenting part of the fetus have a good prognosis in terms of uncomplicated births through natural birth canal (approximately 65% of cases). In 25% of them, it becomes necessary to use obstetric forceps. If the delayed lowering of the fetal part is complicated by its stopping, the prognosis becomes unfavorable: in 43% of cases it ends with a caesarean section operation, in 18% - with obstetric forceps. In addition, in women with delayed fetal passage through the birth canal, who were stimulated with oxytocin or used obstetric forceps, perinatal mortality reached 69%, and a low Apgar score of 32%.

Management of labor with a slow lowering of the fetus

The primary task of management is to exclude such obvious causes of complications, as epidural anesthesia, overdose of sedatives, improper presentation of the fetus and its large size.

In the absence of these factors, a mismatch between the size of the fetus and the pelvis of the mother should be suspected, especially in primiparous women, observed in about 30% of cases. To solve this problem, it is necessary to determine the size of the pelvis using clinical methods (Gillis-Muller method). If there is a discrepancy, you should perform pelvimetry. Radiographic evaluation of pelvic and fetal dimensions is also required in cases when the delay in lowering passes to its full stop, which is observed in the majority of parturient women with slow down and large fetal sizes. Medical measures should be aimed at eliminating the established etiologic factor. With epidural anesthesia or an overdose of sedatives, wait-and-see tactics are used until the period of decrease in the effect of these factors. If there is a discrepancy between the size of the fetus and the pelvis of the mother, delivery by a caesarean section is required, with weak bouts - stimulation with oxytocin.

Caesarean section is also a method of choice in the management of women giving birth with an incorrect presentation of a large fetus.

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