ARRIVE trial findings change obstetric practices, pregnancy outcomes

In the year after the ARRIVE trial, there were more inductions of labor, more deliveries at 39 weeks’ gestation and fewer cesarean deliveries nationwide, according to data published in the American Journal of Obstetrics & Gynecology.

Published in 2018, the ARRIVE trial demonstrated that elective induction of labor at 39 weeks’ gestation led to lower cesarean delivery rates and hypertensive disorders in pregnancy among low-risk, singleton, nulliparous women. The findings were important because cesarean delivery rates are at or near “historical highs” in the United States and other developed nations, and surgical birth is associated with increased rates of maternal and neonatal morbidities, the researchers noted.

“My colleagues and I wanted to determine what trends in obstetric practices were like following publication of the ARRIVE trial,” Laura C. Gilroy, MD, a maternal-fetal medicine fellow at Maimonides Medical Center in Brooklyn, New York, told Healio. “In our own experiences, the desire to offer 39-week labor induction to low-risk nulliparous patients was high.”

“However, the logistics of doing so often limited how often we could offer this intervention to our patients,” Gilroy said. “Since ARRIVE was such an impactful paper when it was published in 2018, we hypothesized that there would be a noticeable change, even within 1 year of its publication.”

Establishing the study cohort

Gilroy and colleagues compared trends in obstetric care and perinatal outcomes in a retrospective cohort of nulliparous women who started prenatal care by 12 weeks of singleton gestation and delivered at 39 weeks or later. The pre-ARRIVE group included 1,966,870 births from 2015 through 2017, and the post-ARRIVE group included 609,322 births from 2019. Data from 2018 were excluded to allow time for ARRIVE findings to influence practice.

The post-ARRIVE group was older (27.4 years vs. 27 years; P < .001), had higher BMIs (24.5 kg/m² vs. 24.1 kg/m²; P < .001), were more likely to be married (61.8% vs. 61.2%; P < .001), more likely to have infertility treatment (2.5% vs. 2%; P < .001) and less likely to be white (60.5% vs. 61.7%; P < .001) compared with the pre-ARRIVE group.

Maternal outcomes

After adjusting for differences, women in the post-ARRIVE group were more likely to undergo induction of labor (36.1% vs. 30.2%; adjusted OR = 1.36; 95% CI, 1.36-1.37) and deliver by 39 weeks and 6 days gestation (42.8% vs. 39.9%; aOR = 1.14; 95% CI, 1.14-1.15). They were also less likely to have a cesarean delivery (27.3% vs. 27.9%; aOR = 0.94; 95% CI, 0.93-0.94).

The rate of labor inductions increased by 5 percentage points during 2019, compared with 1 percentage point per year before the ARRIVE trial. The rate of deliveries by 39 weeks and 6 days of gestation increased by 2 percentage points after ARRIVE, which was higher than the 0.4% yearly increase seen before ARRIVE.

Although rare, women in the post-ARRIVE group were more likely to receive a blood transfusion (0.4% vs. 0.3%; aOR = 1.43; 95% CI, 1.36-1.5) and be admitted to an ICU (0.09% vs 0.08%; aOR = 1.2; 95% CI, 1.09-1.33). However, blood transfusion rates were lower than would be expected based on pre-ARRIVE transfusion trends.

“It was surprising to see that even in adverse outcomes that increased in the post-ARRIVE year, the change was less than what would have been expected based on previously noted trends,” Gilroy said. “Thus, we don't consider the adverse outcomes clinically significant in those instances.”

Neonatal outcomes

Newborns in the post-ARRIVE group were more likely to need assisted ventilation at birth (3.5% vs. 2.8%; aOR = 1.28; 95% CI, 1.26-1.3) and for longer than 6 hours (0.6% vs. 0.5%; aOR = 1.36; 95% CI, 1.31-1.41).

“The 2019 rate of immediate assisted ventilation was higher than expected, compared to the pre-ARRIVE trend,” the researchers wrote. “However, the 2019 rate of assisted ventilation longer than 6 hours was lower than if the pre-ARRIVE trend continued, despite remaining statistically significantly higher when compared to the overall average rate between 2015 and 2017.”

Post-ARRIVE neonates were also more likely to have low 5-minute APGAR scores (0.4% vs. 0.3%; aOR = 0.91; 95% CI, 0.86-0.95), the researchers said.

There were no significant differences between pre- and post-ARRIVE rates of neonatal ICU admission (4.9% for both; aOR = 1.01; 95% CI, 0.99-1.03), neonatal seizures (0.04 for both; aOR = 0.97; 95% CI, 0.84-1.13) or surfactant use (0.07% vs. 0.08%; aOR = 1.05; 95% CI, 0.94-1.17).

“Given that these outcomes were found to be more likely to occur in patients who underwent labor induction as compared to those in spontaneous labor, we posit that the increase in these adverse perinatal outcomes would be expected as labor inductions increased after the ARRIVE publication,” Gilroy and colleagues wrote.

Moving forward, the researchers suggested studies examine how access to elective induction varies across the U.S. and expand upon findings with more available post-ARRIVE data.

“We would like to incorporate 2020 and 2021 data to see how the coronavirus pandemic influenced the provision of induction in low-risk groups as well as other ‘elective’ interventions in obstetrics during this time,” Gilroy said. “We also want to see if there are racial or geographical disparities in who is being offered 39-week labor induction among low-risk individuals.”