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.