Impact of the ARRIVE Trial in Nulliparous Individuals with Morbid Obesity: Interrupted Time Series Analysis.

Objective:  We aimed to examine rates of induction of labor at 39 weeks and cesarean delivery before and after the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial stratified by body mass index (BMI; kg/m²) category.

Study design:  This was a repeated cross-sectional analysis of publicly available U.S. birth certificate data from 2015 to 2021. We limited analyses to nulliparous individuals with a singleton pregnancy, cephalic presentation, without chronic hypertension, diabetes (gestational or pregestational), and fetal anomaly who delivered between 39 and 42 weeks' gestation. The pre-ARRIVE period spanned from August 2016 to July 2018 and the post-ARRIVE period spanned from January 2019 to December 2020. The dissemination period of the ARRIVE trial was from August 2018 to December 2018. Our co-primary outcomes were induction at 39 weeks and cesarean delivery. Our secondary outcomes were overall induction of labor and preeclampsia. We conducted an interrupted time series analysis after stratifying by prepregnancy BMI (<40 or ≥40). Negative binomial regression was used to calculate adjusted incident rate ratios with 95% confidence intervals.

Results:  Of 2,122,267 individuals that were included, 2,051,050 had BMI <40 and 71,217 had BMI ≥40. In individuals with BMI <40, the post-ARRIVE period compared to the pre-ARRIVE period was associated with an increased rate of induction of labor at 39 weeks, a decreased rate of cesarean delivery, and an increased rate of overall induction of labor. In individuals with BMI ≥40, the post-ARRIVE period compared to the pre-ARRIVE period was associated with an increased rate of induction of labor at 39 weeks, an increased rate of overall induction of labor and a decreased rate of preeclampsia; however, the decrease in the rate of cesarean delivery was not significant.

Conclusion:  An increase in induction of labor at 39 weeks' gestation in individuals with BMI ≥40 was not associated with a decrease in the cesarean delivery rate.

Key points: · The ARRIVE trial increased 39-week labor inductions in BMI <40 and ≥40.. · BMI <40 had fewer cesareans; BMI ≥40 showed no significant decrease.. · Offering labor induction is reasonable as cesarean rates didn't increase..