To determine whether the timing of initiation of vaginal misoprostol induction has an effect on delivery mode in nulliparous women.
Retrospective cohort study evaluated nulliparas with singleton gestations who underwent cervical ripening with vaginal misoprostol. Exclusion criteria included multiple gestation, previous delivery, age less than 18 years, Bishop score greater than 7, or induction prior to 39 weeks. Induction for rupture of membranes, chorioamnionitis, oligohydramnios, diabetes, preeclampsia, or growth restriction were excluded. The primary outcome was delivery mode. Chi-squared test was performed to determine if the time of start of induction is associated with cesarean in 6-hour intervals.
226 subjects met inclusion criteria and 107 (47.3%) had a cesarean delivery. 106 patients (46.9%) were scheduled between 6:00pm and 11:59pm, and 48.1% delivered via cesarean. 80 patients (35%) were scheduled between 12:00am and 5:59am, and 52.5% delivered via cesarean. 40 patients (17.6%) were scheduled between 6:00am and 5:59pm, and 37.5% delivered via cesarean. Results of Chi-Square test failed to show an association between time interval induction and delivery mode among 226 subjects (p=0.23). Subgroup analysis was performed on patients with Bishop score less than or equal to 4, and 57.7% delivered via cesarean. Chi-Squared test also failed to show an association between start time and delivery mode.
Timing of cervical ripening with vaginal misoprostol is not associated with delivery mode in uncomplicated, nulliparas after 39 weeks. Scheduling of inductions at the discretion of patient or provider, or based on availability of institutional resources does not increase risk of cesarean delivery.