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Clinical Obstetrics

Poster Session 1

(112) Impact of the ARRIVE Trial on Stillbirth Rates in Nulliparous Individuals

Tuesday, February 13, 2024
10:30 AM – 12:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective:

Following the publication of the ARRIVE trial, rates of induction of labor (IOL) increased, even as early as 37 weeks. We aimed to examine the rate of stillbirth at term before and after the ARRIVE trial.

Study Design:

This was a cross-sectional analysis of US vital statistics Live Birth and Fetal Death certificates data from 2016 to 2020. We limited analyses to nulliparas with singleton gestation and cephalic presentation who delivered at term (37-42 weeks). The pre-ARRIVE period was from Jan 2016 to Dec 2017. The post-ARRIVE trial period was from Jan 2019 to Dec 2020. Stillbirth and induction rates at each gestational age were calculated based on the number of ongoing pregnancies. Modified Poisson regression was used to calculate adjusted relative risks (aRR) with 95% confidence intervals (95%CI). We performed a secondary analysis in nulliparas without hypertension, preeclampsia, diabetes, or fetal anomaly (low-risk group).

Results:

Of 4,077,674 births, 5,200 were stillbirths during our study period. There were 2,087,960 births in the pre-ARRIVE period and 1,989,714 in the post-ARRIVE period. Compared to the pre-ARRIVE period, the rate of stillbirths, per 1000 births, in the post-ARRIVE period was significantly lower at term (1.4 vs. 1.2; aRR 0.84 [95% CI 0.79-0.89]), at 37 weeks (0.4vs. 0.3; aRR 0.79 [0.71-0.88]), and at 38 weeks (0.4 vs. 0.3; aRR 0.89 [0.80-0.95]) (Table 1). However, the change in stillbirth rates at 39 weeks and 40-42 weeks were not statistically significant. Rates of IOL increased at all gestational ages. The findings were similar in low-risk individuals. We estimated that 228 additional IOL were needed to prevent 1 additional stillbirth at 37 weeks whereas 5234 additional IOL were needed at 39 weeks.

Conclusion:

Despite increased rates of IOL at all gestational ages, stillbirth rates only decreased at 37-38 weeks. An increase in IOL at 39 weeks was not large enough to impact the stillbirth rate at 39 weeks or greater.