Induction of labor at 39 weeks' decreases cesareans without increase in perinatal morbidity

Reference

Grobman WA, Rice MM, Reddy UM, et al, for the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network. Labor induction versus expectant management in low-risk nulliparous women. N Engl J Med 2018;379(6):513-523.

Synopsis

In this large multicenter randomized controlled trial routine labor induction of low-risk nulliparous women at 39 weeks of gestation (n = 3062) was compared with expectant management until at least 40 weeks 5 days of gestation (n = 3044). Although it was not feasible to mask the study, randomization was concealed and outcome assessment from the medical records was masked. Eligible women had a single live fetus in vertex presentation with no contraindication to vaginal delivery and no maternal or fetal indication for delivery before 40 weeks 5 days. Enrollment took place between 38 weeks 0 days and 38 weeks 6 days. Women in labor or with premature rupture of membranes were excluded. The enrollment rate was relatively low: 27% of eligible women. Dating of pregnancy had to be definite, based either on certain date of last menstrual period and confirming ultrasound before 21 weeks' gestation or ultrasound only dating before 14 weeks' gestation. There was no specific induction protocol. Less than 10% of women in each group withdrew or were lost to follow-up. The primary perinatal outcome was a composite of perinatal death or severe neonatal complications, including a need for respiratory support within 72 hours after birth, an Apgar score of less than 3 at 5 minutes, hypoxic-ischemic encephalopathy, seizure, infection, meconium aspiration syndrome, birth trauma, intracranial or subgaleal hemorrhage, or hypotension requiring vasopressor support. This primary outcome was not significantly different between groups, with trend favoring induction: 4.3% in the induction group vs 5.4% in the control group (relative risk [RR] 0.80; 95% CI 0.64 - 1.00; P = .049). The primary outcome for women was cesarean delivery rate, which was decreased in the induction group: 18.6% vs 22.2% (RR 0.84; 0.76 - 0.93; P < .001; number needed to treat = 28; 8 - 64). Although the decrease in cesarean delivery rate was statistically significant, it was clinically modest. Prespecified subgroup analyses were consistent with the main outcomes and included race ethnic group, age younger versus older than 35 years, body mass index less than or greater than 30, Bishop score less than 5 versus 5 or higher, and specialty of the admitting provider (obstetrician-gynecologist, maternal fetal medicine, family medicine, or midwife). Multiple additional analyses of secondary outcomes did not affect the conclusion that induction at 39 weeks' is a relatively safe practice.