Background: Recent evidence supports elective induction of labor at 39 weeks in low-risk pregnancies to improve maternal and perinatal outcomes. This evidence includes the ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management). However, concerns have been raised on the external validity of the ARRIVE trial, especially with regard to the demographic and clinical characteristics of the pregnant women recruited.
Objective: This study compared the outcomes in a cohort of consecutive pregnant women, who fulfilled the criteria of the ARRIVE trial and were managed expectantly in an Italian referral academic hospital, with those reported in the expectant and induction arms of the ARRIVE trial.
Study design: This was a retrospective single-center study. Consecutive low-risk nulliparous women who fulfilled the ARRIVE trial criteria were evaluated for eligibility at 36-38 weeks of gestation. Those who neither developed complications nor delivered spontaneously before 39 weeks were eligible for this comparative analysis. Maternal and fetal growth and wellbeing were screened and monitored from 36 to 38 weeks of gestation.
Results: A total of 1696 patients met the established criteria at recruitment. Of these, 343 spontaneously delivered in <39 weeks, 82 delivered because of maternal indication, and 37 for fetal indication. A total of 1234 pregnant women were eligible for comparison with the elective induction and the expectant management groups of the ARRIVE trial. The socioeconomic status was significantly better, maternal age was significantly higher, and body mass index was significantly lower in our cohort. Cesarean section rate in our cohort was lower than that of the expectant group of the ARRIVE trial (18.7 vs. 22.2%; p = 0.02) and similar to that of the elective induction group (18.7 vs. 18.6%). A new diagnosis of hypertensive disorders during expectant management was noted in 1.6% in our cohort vs. 14.1% in the ARRIVE arm. Among the different obstetric outcomes, only the prevalence of postpartum hemorrhage was not significantly lower in our cohort. The primary perinatal composite outcome was significantly better in our cohort than in both arms of the ARRIVE trial (2.1 vs. 5.4% in the expectant group and 4.3% in the induction group). We did not record cases with an Apgar score ≤ 3 or hypoxic-ischemic encephalopathy.
Conclusion: In our cohort, expectant management in low-risk pregnancies with late preterm screening of feto-maternal well-being seemed to achieve better maternal and perinatal outcomes than a universal policy of induction at 39 weeks. The results of the ARRIVE trial should be carefully evaluated in different demographic and clinical settings and cannot be extended to the general population.
Keywords: Induction of labor; elective induction of labor; low-risk pregnancy; obstetric outcome; perinatal outcome.