Induction of Labor at 40 Weeks of Gestation after Dissemination of the ARRIVE Trial

The ARRIVE trial showed that induction of labor in low-risk nulliparous individuals at 39 weeks reduced cesarean delivery. We sought to determine whether publication of the ARRIVE trial was associated with changes in the rate of induction of labor at 40 weeks, and if so, whether similar changes were seen in the rate of cesarean delivery.

This was a repeated cross-sectional analysis using US natality data from February 2017 to August 2019. Low-risk nulliparous individuals delivering a non-anomalous, cephalic, singleton infant were included; exclusion criteria included hypertension, diabetes, or small-for-gestational age infant. The primary outcome was induction of labor at 40 weeks. Secondary outcomes included cesarean delivery and a composite of adverse neonatal outcomes. A population-level interrupted time series analysis was performed. The pre-period ran from February 2017 to January 2018, the dissemination period from February to August 2018, and the post-period from September 2018 to August 2019.

The study included 843,133 individuals (339,978 in the pre-period; 190,479 in the dissemination or washout period; 312,676 in the post-period). The rate of induction of labor at 40 weeks increased from a predicted rate of 18.7% to an observed rate of 20.2% (IRR, 1.08, 95% CI: 1.05-1.12) in the post-period. The rate of cesarean delivery and adverse neonatal outcomes in the cohort did not change at the start of the post-period (cesarean delivery: 25.3% predicted vs. 25.2% observed, IRR, 1.00, 95% CI: 0.96-1.03; adverse neonatal outcome: 5.3% predicted vs. 5.0% observed, IRR, 0.95, 95% CI: 0.87-1.02).

Dissemination of the ARRIVE trial was associated with an increase in the rate of induction at 40 weeks among patients who remained pregnant after 39 weeks. However, there was no population-level decrease in cesarean delivery, suggesting that the benefits of induction of labor may not extrapolate to this cohort.

· The ARRIVE trial increased low-risk induction of labor at 40 weeks of gestation.. · Increasing 40-week induction rates did not correspond to lower rates of cesarean delivery.. · Offering induction at 40 weeks is reasonable given no associated increase in adverse outcomes..