Context: After 41 weeks, the labor induction term varies according to countries and obstetrical teams. The French recommendations are not to exceed 41 weeks 6 days. However, there are no data on the percentage of nulliparous women with an unfavorable cervix at 41 weeks going into spontaneous labor within five or six days.
Objective: The objective was to establish the rate of spontaneous labor within five days amongst nulliparous women with an unfavorable cervix at 41 weeks, and to identify the maternal and obstetrical factors associated with this spontaneous labor.
Materials and methods: Retrospective study in a University Hospital Maternity between January 1st and December 31st 2017. All nulliparous women with a cephalic fetal presentation and unfavorable cervix at 41 weeks (Bishop ≤ 3) were included. The maximum term for induced labor was set at 41 weeks 5 days. The population was divided into two groups: spontaneous labor and induced labor (induction between 41 weeks and 41 weeks 4 days for medical indications or maternal wish and induction at 41 weeks 5 days for full term). The maternal and obstetrical characteristics of the two groups at 41 weeks were compared as well as the maternal and neonatal outcomes.
Results: The rate of spontaneous labor among the 269 women included was 38.3% (n = 103/269). At 41 weeks, the presence of painful uterine contractions and a Bishop score of 3 were associated with spontaneous labor within five days (p < 0.01). The Bishop score criteria most associated with spontaneous labor were cervical dilation and fetal station. The cesarean delivery rate was 20.4% in the group of women with spontaneous labor versus 41.0% in the group of induced labor (p < 0.01). There were no differences between the two groups in terms of neonatal outcome.
Conclusion: Among nulliparous women with an unfavorable cervix at 41 weeks, almost 40 % will have a spontaneous onset of labor within five days. The only factors found to be associated with this onset of labor are the presence of painful uterine contractions and a higher Bishop score at 41 weeks.