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Stopping the descent of the fetus anteriorly

 
, medical expert
Last reviewed: 04.07.2025
 
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As is known, the most significant descent of the presenting part of the fetus occurs at the end of the first and especially in the second stage of labor. Therefore, the impossibility of further advancement of the fetus, the stoppage or slowing down of the descent are typical disorders of the second stage of labor. The stoppage of the descent is noted when the fetus does not advance along the birth canal for 1 hour, which can be established by the results of vaginal examinations performed at the appropriate time interval.

Diagnostics. To establish a diagnosis, it is necessary to conduct at least 2 vaginal examinations. Determining the nature of the fetus's progress in the mother's pelvis is complicated by the fact that by the end of labor, the shape of the fetus's head (configuration) changes, which increases the likelihood of errors. In many cases, a vaginal examination gave the impression that positive dynamics had occurred, whereas this was only due to the appearance of a birth tumor or the configuration of the head.

Errors of this kind are so common that E. Friedman recommends that all women in labor with suspected abnormalities in fetal descent determine the height of the fetal presenting part simultaneously during external obstetric and vaginal examinations.

To determine the nature of the descent of the presenting part of the fetus during an external obstetric examination, the 1st and 2nd Leopold maneuvers should be performed and the height of the presenting part of the fetus should be estimated within the range of values from -5 (the head is mobile) to +5 (the head is deep in the small pelvis). This method is less accurate compared to the assessment of the position of the presenting part of the fetus, carried out using a vaginal examination. By using both methods simultaneously, errors arising due to the configuration of the fetal head can be minimized.

Frequency: Arrest of descent of the presenting part of the fetus occurs in approximately 5-6% of births.

Causes: There are three main causes of arrest of descent: mismatch between the size of the fetus and the mother's pelvis, abnormal presentation of the fetus, and regional anesthesia.

In primiparous women, the discrepancy between the sizes of the fetus and the mother's pelvis causes this complication in more than 50% of cases. This is observed even more often if the arrest occurs with a high position of the presenting part of the fetus or the woman in labor receives stimulation with oxytocin. E. Friedman et al. (1978) reported that when epidural anesthesia was administered, 80.6% of primiparous women subsequently experienced an arrest in the descent of the presenting part of the fetus. Thus, epidural anesthesia serves as an additional factor contributing to the development of this complication.

Similarly, abnormal fetal presentation (with the occiput facing backwards) was noted in 75.9% of women with cessation of fetal descent. However, almost all primiparous women with abnormal fetal presentation had other factors acting simultaneously. In this regard, it is difficult to single out the independent role of abnormal fetal presentations as an etiologic factor in cessation of descent of the presenting part of the fetus.

In multiparous women with cessation of fetal progression through the birth canal, the frequency of discrepancy between the sizes of the fetus and the mother's pelvis is only 29.7%. The frequency of abnormal fetal presentation or the use of epidural anesthesia is the same as in primiparous women.

Prognosis. In pregnant women with arrest of descent of the presenting part of the fetus, the prognosis should be judged with caution. This is mainly due to the fact that in this anomaly of labor, a very common etiologic factor is the discrepancy between the sizes of the fetus and the mother's pelvis. E. Friedman et al. (1978) showed that 30.4% of women in labor with arrest of descent of the fetus required a cesarean section, 37.6% - the application of obstetric forceps (cavity), 12.7% - rotation of the head in forceps; in 5.1% of women, the use of forceps was unsuccessful.

Below are the most important prognostic signs in women giving birth with arrest of the presenting part of the fetus:

  • the level of the position of the presenting part of the fetus at the moment of stopping (the higher the position, the greater the likelihood of a discrepancy between the size of the fetus and the mother's pelvis);
  • duration of the arrest (the longer it is, the higher the probability of a discrepancy between the sizes of the fetus and the mother’s pelvis);
  • the nature of the descent of the presenting part of the fetus after stopping (if the speed of its descent after stopping is the same or greater than before, a good prognosis can be given for normal atraumatic labor).

Arrest of fetal descent is associated with significant maternal and perinatal morbidity, regardless of whether surgical intervention is required. The most common complication is postpartum hemorrhage (12.5% of cases). Threatened fetal condition, judging by low Apgar scores, is a common complication (21.9%). Complicated delivery of the shoulder girdle (shoulder dystopia) and the associated increased morbidity (Erb's palsy, clavicle fracture, fetal trauma, etc.) are observed in 14.1% of cases.

Management of labor when the descent of the presenting part of the fetus has stopped

Once the diagnosis of fetal presenting part descent arrest has been established, the first steps should be aimed at identifying the etiologic factors. However, the presence of such obvious causes as epidural anesthesia or abnormal fetal presentation should not prevent the physician from assessing the ratio of fetal and maternal pelvic sizes. The Gillies-Muller test should be used, and if free progression of the fetal presenting part is recorded, excluding a size discrepancy, other factors can be sought. If the Gillies-Muller test is negative, pelvimetry should be performed immediately, and if a size discrepancy between the fetus and the maternal pelvis is detected, a cesarean section should be performed.

If clinical and pelvimetry data exclude fetal-pelvic size discrepancy, further management involves observation of the woman in labor until the effect of sedatives wears off, regional anesthesia (if used), or uterine stimulation. Both approaches require careful monitoring of the mother and fetus (intrauterine pressure, fetal head pH, direct fetal electrocardiography). In the absence of disproportion between the fetal head and the maternal pelvis, oxytocin stimulation is indicated, starting with small doses (0.5-1.0 mIU/min) with a gradual increase at intervals of at least 20 minutes. The effect of stimulation is observed within the next 1-1.5 hours. If such an effect is not noted within 2 hours after the start of treatment, the situation should be seriously re-evaluated so that a possible fetal-pelvic size discrepancy does not remain unrecognized.

If a disproportion between the size of the fetus and the mother's pelvis is detected, a cesarean section is required without further attempts at vaginal delivery.

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