Objective: Elective induction of labor versus expectant management at 39 weeks gestation in low-risk nulliparous patients was shown in the ARRIVE randomized trial of over 6000 patients to decrease risks of cesarean delivery without significant change in the composite perinatal outcome. We aimed to pragmatically analyze the effect of offering elective induction of labor (eIOL) to all low-risk patients.
Methods: Retrospective cohort study of low-risk nulliparous and multiparous patients delivering live, non-anomalous singletons at a single center at greater than or equal to 39 0/7 weeks gestational age. Those with prior or planned cesarean delivery, ruptured membranes, medical comorbidities, or contraindications to vaginal delivery were excluded. Patients were categorized as before (pre-eIOL; 1/2012-3/2014) or after (post-eIOL; 3/2019-12/2021) an institution-wide policy offering eIOL at 39 0/7 weeks. Births occurring April 2014 to December 2018 were allocated to a separate cohort (during-eIOL) given increased exposure to eIOL as our center recruited participants for the ARRIVE trial. The primary outcome was cesarean birth. Secondary outcomes included select maternal (e.g. chorioamnionitis, operative delivery, postpartum hemorrhage) and neonatal morbidities (e.g. birthweight, small- and large-for gestational age, hypoglycemia). Characteristics and outcomes were compared between the pre and during-eIOL, and pre and post-eIOL groups; adjusted OR (95% CI) were calculated using multivariable regression. Subgroup analysis by parity was planned.
Results: Of 10,758 patients analyzed, 2521 (23.4%) were pre-eIOL, 5410 (50.3%) during-eIOL, and 2827 (26.3%) post-eIOL. Groups differed with respect to labor type, age, race/ethnicity, marital and payor status, and gestational age at care entry. Post-eIOL was associated with lower odds of cesarean compared to pre-eIOL (aOR 0.83 [95% CI 0.72-0.96]), which was even lower among those specifically undergoing labor induction (aOR 0.58 [0.48-0.70]. During-eIOL was also associated with lower odds of cesarean compared to pre-eIOL (aOR 0.79 [0.69-0.90]). Both during and post-eIOL groups were associated with higher odds of chorioamnionitis, operative delivery, and hemorrhage compared to pre-eIOL. However, only among post-eIOL were there fewer neonates weighing ≥4000 g, large-for-gestational age infants, and neonatal hypoglycemia compared to pre-IOL.
Conclusion: An institutional policy offering eIOL at 39 0/7 to low-risk patients was associated with a lower cesarean birth rate, lower birthweights and lower neonatal hypoglycemia, and an increased risk of chorioamnionitis and hemorrhage.
Keywords: Cesarean delivery; chorioamnionitis; hemorrhage; neonatal hypoglycemia.