Nationwide assessment of labor induction at full-term for low-risk pregnancy in the United States from 2018 to 2022

Role of labor induction requiring cervical preparation for full-term, low-risk pregnant patients is under active investigation. The objective of this study was to describe nationwide temporal trends, characteristics, and outcomes associated with labor induction requiring cervical preparation at full-term gestation for low-risk pregnant patients in the United States. This cross-sectional study queried the Agency for Healthcare Research and Quality mechanism's Healthcare Cost and Utilization Project National Inpatient Sample. Study population included 5,003,348 hospital deliveries at 39-406/7 weeks' gestation for singleton, cephalic low-risk pregnancy from 2018 to 2022, excluding historically known presumed pre-labor pregnancy risk factors. Exposure was labor induction status, defined as the performance of cervical preparation (ripening or mechanical dilation), with or without adjunctive intervention (artificial rupture of membranes or oxytocin administration). Main outcome measures were set as cesarean delivery as the primary outcome; induction failure, chorioamnionitis, umbilical cord prolapse, in-labor uterine rupture, postpartum hemorrhage, severe maternal morbidity and mortality as the secondary outcomes, assessed with multivariable generalized linear model. A total of 618,785 (12.4%) deliveries had labor induction requiring cervical preparation. The rate increased from 8.8 to 14.4% between QT1/2018-QT2/2020 (P-trend < .001), at which the rate started gradually decreasing when the COVID-19 pandemic occurred (14.4% at QT2/2020 to 13.4% at QT4/2022, P-trend = .04). The majority of cervical preparation was ripening alone (69.9%), followed by mechanical dilation alone (20.7%) and both ripening and mechanical dilation (9.4%). During the 5-year study period, cervical preparation with mechanical dilation alone (14.4% to 26.9%) and both ripening and mechanical dilation (4.6% to 11.4%) increased (both, P-trend < .001); adjunctive use of both oxytocin and artificial rupture of membranes (18.7% to 27.0%) and oxytocin alone (15.0% to 18.8%) increased while artificial rupture of membranes alone decreased (29.5% to 23.0%) (all, P-trend < .001). When compared to 4,384,563 deliveries without labor induction cervical preparation, induction was associated with cesarean delivery (17.1% vs 9.2%, adjusted-incidence rate ratio aIR 1.75, 95% confidence interval CI 1.74-1.76), chorioamnionitis (3.2% vs 1.9%, aIR 1.67, 95%CI 1.64-1.69), umbilical cord prolapse (0.2% vs 0.1%, aIR 1.67, 95%CI 1.58-1.77), in-labor uterine rupture (21.8 vs 7.8 per 100,000, aIR 2.66, 95%CI 2.17-3.25), postpartum hemorrhage (5.7% vs 3.9%, aIR 1.42, 95%CI 1.40-1.44), severe maternal morbidity (0.4% vs 0.2%, aIR 1.61, 95%CI 1.54-1.68), and maternal mortality (4.8 vs 0.7 per 100,000, aIR 7.34, 95%CI 4.37-12.33). In conclusion, this nationwide cross-sectional assessment suggests the increasing trend of full-term labor induction for study-defined low-risk pregnancy may have stopped during the COVID-19 pandemic in the United States. The observed association with cesarean delivery and adverse outcomes related to labor induction requiring cervical preparation warrant further investigation.