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Prolonged deceleration phase
Last reviewed: 04.07.2025
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The prolonged slowing phase is characterized by an increase in its duration in primiparous women by more than 3 hours, and in multiparous women by more than 1 hour. Under normal conditions, the average duration of the slowing phase is 54 minutes in primiparous women and 14 minutes in multiparous women.
Diagnostics. To diagnose a prolonged slowing phase, at least 2 vaginal examinations must be performed with an interval between them of 3 hours in primiparous women and 1 hour in multiparous women. More than two examinations are usually performed during the time required to establish a diagnosis.
During normal labor, the deceleration phase is difficult to detect without frequent vaginal examinations at the end of the active phase. However, if abnormalities occur in the deceleration phase, it is easy to detect if it is not masked by the development of other concomitant labor abnormalities. Such situations are common; in approximately 70% of cases, a prolonged deceleration phase occurs along with a prolonged active phase of cervical dilation or with an arrest in the progression of the fetus through the birth canal. In such cases, the diagnosis is not always possible, since most attention is paid to determining concomitant disorders.
Frequency. This pathology can complicate up to 5% of births. In any case, it is the rarest of all labor anomalies.
Causes. The most frequent cause of the prolonged deceleration phase is abnormal fetal presentation. In 40.7% of multiparous women, the fetus was presented cephalically with the occiput facing backwards, and in 25.4%, the fetus was presented transversely. Their frequency in primiparous women was 26.3% and 60%, respectively. The discrepancy between the sizes of the fetus and the mother's pelvis was the etiologic factor in approximately 15% of women with this labor disorder. The prolonged deceleration phase is often observed in labor complicated by difficult passage of the fetal shoulder girdle (dystopia).
Prognosis. According to E. Friedman (1978), more than 50% of primiparous women and about 30% of multiparous women require delivery by means of abdominal obstetric forceps. The use of forceps (rotation during application of forceps) was required by 40% of primiparous women and 16.9% of multiparous women; cesarean section was performed in 16.7% and 8.5% of multiparous women, respectively. The prognosis for this anomaly is worse in women with their first pregnancy.
Conducting a prolonged deceleration phase
It depends primarily on the nature of the descent of the presenting part of the fetus. If a longer deceleration is observed with a completely appropriate descent of the presenting part of the fetus (especially if it is below the level of the iliac spines of the pelvis), then the presence of a disproportion is unlikely and the prognosis for vaginal delivery is favorable. If the deceleration phase develops with a high-standing presenting part (especially when it is accompanied by a stop in the descent), then the situation is quite serious - a discrepancy between the sizes of the fetus and the mother's pelvis is very likely.
In the first case - stopping in position +1 or lower position - the most common causes are incorrect presentation of the fetus (the occiput is turned backwards, the head is in a transverse position), an overdose of sedatives, and epidural anesthesia.
Management usually involves gentle stimulation with oxytocin or observation of the pregnant woman while waiting for the cessation or reduction of the effects of sedatives or anesthesia.
The second group of women in labor - the presenting part of the fetus is above 0 - requires urgent pelvimetry; further development of labor is allowed only if there is no discrepancy between the size of the fetus and the pelvis of the woman in labor.
The number of previous births a woman has should not affect the management plan. With this type of labor dysfunction, the frequency of discrepancies is almost the same in primiparous (15.8%) and multiparous (15.3%) women.
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