Elective Induction of Labor in Nulliparas: has the ARRIVE trial changed obstetric practices and outcomes?


      In 2018, the ARRIVE trial (Grobman et al. N Engl J Med. 2018) reported that 39-week elective labor induction in nulliparas decreased cesarean birth and pre-eclampsia rates compared with expectant management. Our hypothesis was that this publication had an immediate impact on induction practices and decreased cesarean birth and preeclampsia rates over time.

      Study Design

      An interrupted time series (ITS) analysis using clinical data on consecutive nulliparous singleton births at ≥39 weeks’ gestation in 13 US hospitals (Jan 2016-Dec 2019) was performed. Unlike “before and after” studies, ITS analyses account for pre-existing trends when evaluating the effect of an intervention. The ARRIVE trial publication date (08/09/2018) was used as the intervention time point. Time trends were modeled using 4-weekly data with a trend pre-ARRIVE, a level shift at the time of publication, and a post-ARRIVE trend change. A modified Poisson regression model was used. Elective induction was the primary outcome. Cesarean birth and gestational hypertensive disorders were secondary outcomes.


      A total of 23956 births were included (15917 pre-ARRIVE and 8039 post-ARRIVE). Mean maternal age was 28.5 (SD 5.5) and mean BMI was 31.1 (SD 5.9). Total and elective induction rates, and time on L&D were higher in the post-ARRIVE period (Table 1). Interrupted time series analysis showed the onset of the ARRIVE trial was associated with a statistically significant level change increase in elective labor induction (RR 1.51; 95% CI 1.15, 1.99) (Figure 1). No statistically significant decreases were observed in the rates of pre-eclampsia or cesarean birth rates.


      This study suggests that publication of a single randomized control trial (ARRIVE) rapidly influenced obstetric practice resulting in increased elective labor induction among nulliparas. In our population, decreases in cesarean birth and preeclampsia have not been realized raising questions about the applicability of the ARRIVE trial findings to a general obstetric population.
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