Labor Induction versus Expectant Management in Low-Risk Nulliparous Women

Abstract

Background: The perinatal and maternal consequences of induction of labor at 39 weeks among low-risk nulliparous women are uncertain.

Methods: In this multicenter trial, we randomly assigned low-risk nulliparous women who were at 38 weeks 0 days to 38 weeks 6 days of gestation to labor induction at 39 weeks 0 days to 39 weeks 4 days or to expectant management. The primary outcome was a composite of perinatal death or severe neonatal complications; the principal secondary outcome was cesarean delivery.

Results: A total of 3062 women were assigned to labor induction, and 3044 were assigned to expectant management. The primary outcome occurred in 4.3% of neonates in the induction group and in 5.4% in the expectant-management group (relative risk, 0.80; 95% confidence interval [CI], 0.64 to 1.00). The frequency of cesarean delivery was significantly lower in the induction group than in the expectant-management group (18.6% vs. 22.2%; relative risk, 0.84; 95% CI, 0.76 to 0.93).

Conclusions: Induction of labor at 39 weeks in low-risk nulliparous women did not result in a significantly lower frequency of a composite adverse perinatal outcome, but it did result in a significantly lower frequency of cesarean delivery. (Funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development; ARRIVE ClinicalTrials.gov number, NCT01990612 .).

Figure 1.. Eligibility, Randomization, Delivery, and Assessment.

Per-protocol delivery in the induction group was defined as electively induced labor from 39 weeks 0 days to 39 weeks 4 days or spontaneous labor or medically indicated delivery on or before 39 weeks 4 days (this also included delivery delayed past 39 weeks 4 days because of a new medical indication that had developed). Per-protocol delivery in the expectant-management group was defined as induction from 40 weeks 5 days to 42 weeks 2 days or spontaneous or medically indicated delivery on or before 42 weeks 2 days.

Figure 2.. Prespecified Subgroup Analyses According to Maternal Baseline Variables.

The primary outcome was a composite of perinatal death or severe neonatal complications and consisted of one or more of the following during the antepartum or intrapartum period or during the delivery hospitalization: perinatal death, the need for respiratory support within the first 72 hours after birth, Apgar score of 3 or less at 5 minutes, hypoxic–ischemic encephalopathy, seizure, infection (confirmed sepsis or pneumonia), meconium aspiration syndrome, birth trauma (bone fracture, neurologic injury, or retinal hemorrhage), intracranial or subgaleal hemorrhage, or hypotension requiring vasopressor support. Race was reported by the participant; “other” race or ethnic group includes other, unknown, or more than one race or ethnic group. Modified Bishop scores range from 0 to 12, with lower scores associated with a higher chance of cesarean delivery. The body-mass index (BMI) is the weight in kilograms divided by the square of the height in meters.