Passive second stage of labor: Does a fourth hour increase maternal morbidity in nulliparous patients at term with...

Prolonging the passive second stage of labor could increase vaginal birth rate, but the data concerning maternal and fetal morbidity are contradictory. The French guidelines did not specify a maximum duration of the passive second stage. Our objective was to assess if allowing a 4th hour after full dilatation before pushing increased maternal morbidity, compared to 3 h after full dilatation.

This single-center, retrospective, observational cohort study took place from January 1-December 31, 2020, in a tertiary maternity unit. All consecutive term nulliparous women who delivered under epidural anesthesia and without pathological fetal heart rate and reaching a second-stage passive phase of labor lasting at least 3 h were included. We compared 2 groups according to the duration of the passive second stage: "3-hour group" and "4-hour group". In the "3-hour group," featuring a second-stage passive phase of up to 3 h, pushing is initiated for favorable conditions, while a cesarean section is performed if conditions are deemed unfavorable. In the "4-hour group", obstetric conditions not justifying immediate pushing after three hours, and the obstetric team believed that an additional hour of expectant management could lead to a successful vaginal delivery. The principal endpoint was a composite criterion of maternal morbidity including obstetric anal sphincter injuries, postpartum hemorrhage, transfusion and intrauterine infection.

We included 111 patients in the "4-hour group" and 349 in the "3-hour group". Composite maternal morbidity did not increase in the "4-hour group" compared to the "3-hour group" (21 (18.9 %) versus 61 (17.5 %); p = 0.73). Neonatal morbidity was similar between the two groups. In the "4-hour group, 91 (82 %) patients had vaginal deliveries", 62 (55,9 %) by spontaneous vaginal delivery and 29 (26,1 %) with instrumental assistance.

For selected patients, waiting for 4 h at full dilation can be beneficial due to the high rate of vaginal delivery and low incidence of maternal and fetal complications.