Inductions of labor (IOL) vary in their duration and the effects of that variation are largely unknown. This study aims to assess the impact of IOL duration on maternal morbidity.METHODS:
This retrospective cohort study included all nulliparous women with non-anomalous, singleton, vertex pregnancies undergoing IOL at a tertiary-care academic hospital in 2015. IOL duration was calculated as time from administration of first induction agent to delivery. The primary outcome was maternal composite morbidity: third or fourth degree perineal laceration, postpartum hemorrhage, blood transfusion, peripartum infection, uterine rupture, shoulder dystocia, retained placenta, and/or postpartum readmission. Secondary outcome was mode of delivery. The risk of adverse outcomes was stratified by IOL duration.RESULTS:
Four hundred twenty women were included. IOL duration exceeding 24 hours was associated with increased risk of composite maternal morbidity (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.1–2.7) but that risk did not persist among IOL exceeding 36 hours. One hundred twenty women (28.6%) had a cesarean section. IOL duration exceeding 24 hours was associated with increased risk of CD (OR 3.2, 95% CI 2.0–5.4) which persisted at 36, 48, and 60 hours (OR 2.9 [1.8–4.5], OR 2.8 [CI 1.7–4.8], OR 2.3 [CI 1.1–5.0]). IOL duration was not associated with increased risk of operative delivery.CONCLUSION:
While increasing IOL duration is associated with increased risk of maternal morbidity at 24 hours, that risk does not persist beyond 36 hours. Conversely, IOL duration longer than 24 hours is associated with increased risk of CD. These data may inform decision-making surrounding prolonged IOL.