Impact of the ARRIVE Trial on Stillbirth Rates in Nulliparous Individuals

Abstract

Objective We aim to examine the population-level rates of induction, stillbirth, perinatal mortality, and neonatal death before and after the ARRIVE (A Randomized Trial of Induction Versus Expectant Management) trial. Study Design This study was a cross-sectional analysis of publicly available U.S. Live Birth data linked with Infant Death and Fetal Death certificate data from National Vital Statistics Online. We limited analyses to nulliparous individuals with singleton pregnancy and cephalic presentation who delivered at 39 weeks or greater. The pre- and post-ARRIVE periods spanned from August 2016 to July 2018, and from January 2019 to December 2020, respectively. Our primary outcome was a stillbirth. Secondary outcomes included induction of labor, perinatal mortality, and neonatal death. Outcomes were compared between the pre- and post-ARRIVE periods. Modified Poisson regression was used to calculate adjusted relative risks (aRRs). Results Of 2,817,071 births, there were 1,454,346 births in the pre-ARRIVE period and 1,362,725 in the post-ARRIVE period; there were 1,196 and 1,062 stillbirths in the pre- and post-ARRIVE periods, respectively. Compared to the pre-ARRIVE period, the post-ARRIVE period was not associated with a significant decrease in the risk of stillbirth at 39 weeks or greater (aRR 0.92 [95% confidence interval {95% CI} 0.85–1.00]) and stillbirth at 40 weeks or greater (aRR 0.92 [95% CI 0.82–1.04]). Compared to the pre-ARRIVE trial period, the post-ARRIVE trial was associated with increased rates of induction of labor at 39 weeks (aRR 1.37 [95% CI 1.37–1.38]) and 40 weeks (aRR 1.24 [95% CI 1.24–1.25]. Similar to stillbirth, there was no significant decrease in the risk of perinatal mortality at 39 weeks or greater or 40 weeks or greater. There was also no statistically significant change in neonatal death rates at 39 weeks or greater or at 40 weeks or greater. Conclusion The increase in induction of labor at 39 weeks was not large enough to impact the stillbirth rate at 39 weeks or greater. Key Points