Abstract
Objective
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.
Study Design
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.
Results
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).
Conclusion
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.
Key Points
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The ARRIVE trial increased low-risk induction of labor at 40 weeks of gestation.
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Increasing 40-week induction rates did not correspond to lower rates of cesarean delivery.
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Offering induction at 40 weeks is reasonable given no associated increase in adverse
outcomes.
Keywords
induction of labor - ARRIVE trial - interrupted time series - cesarean delivery
