(553) Impact of induction versus expectant management on cesarean rates in nulliparous women with closed cervix

Objective:
To evaluate whether induction of labor at 39 weeks versus expectant management in low-risk nulliparous women with a closed cervix on exam at 37-38 weeks is associated with an increased risk of cesarean delivery (CD).

Study Design:
This is a secondary analysis of a multicenter randomized trial of induction of labor at 39 weeks compared with expectant management in low-risk nulliparous patients (ARRIVE). Only participants with a cervical dilation ≤0.5 cm within 72 hours before or 24 hours after randomization (37w4d-38w6d) were included. Primary outcome was rate of CD. Secondary outcomes were maternal (modified Bishop score on L&D, duration of labor, rate of operative vaginal delivery, chorioamnionitis, postpartum infection, postpartum hemorrhage, prolonged postpartum hospitalization) and neonatal (composite of adverse outcomes). Modified Poisson and log-linear regressions were performed to estimate adjusted relative risks; penalized methods addressed rare events, and Chi-square and Mann-Whitney U tests were used for group comparisons.

Results:
2399 patients were included: 1205 in induction (IOL) and 1194 in expectant management (EM). Baseline demographics were similar (IOL v EM), except for Hispanics (35.9% v 30.7%, p < 0.01), BMI ≥30 (23.3% v 27.6%, p < 0.05), and history of loss (21.5% v 26.9%, p < 0.01). After adjustment for significant variables, rate of CD in IOL was significantly lower than in EM (24.9% v 30.0%, aRR 0.85 [95% CI: 0.75–0.97]). The primary indication for CD were similar (IOL v EM): non-reassuring fetal status (52.0% v 47.3%, p 0.31) and dystocia/maternal exhaustion (39.4% v 46.0%, p 0.10). As for secondary outcomes, EM had higher Bishop score on admission, higher rates of SROM, and shorter duration between admission and delivery, without increased risk of adverse maternal or neonatal outcomes (Table).

Conclusion:
Women with a closed cervix in the early term period have a lower CD rate when induced at 39 weeks. This finding can help counsel patients with a closed cervix in clinic that induction of labor at 39 weeks does not increase CD risk.