William A. Grobman, M.D., Madeline M. Rice, Ph.D., Uma M. Reddy, M.D., M.P.H., Alan T.N. Tita, M.D., Ph.D., Robert M. Silver, M.D., Gail Mallett, R.N., M.S., C.C.R.C., Kim Hill, R.N., B.S.N., Elizabeth A. Thom, Ph.D., Yasser Y. El-Sayed, M.D., Annette Perez-Delboy, M.D., Dwight J. Rouse, M.D., George R. Saade, M.D., et al., for the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network*

A previous randomized trial conducted in the United Kingdom compared labor induction at 39 weeks of gestation with expectant management among 619 women who were 35 years of age or older and who had no other indication for delivery at 39 weeks of gestation.12 The frequency of cesarean delivery was similar in the two groups (relative risk, 0.99; 95% confidence interval [CI], 0.87 to 1.14), although several aspects of the trial, including a rate of operative vaginal delivery (i.e., vaginal delivery with the use of forceps or vacuum) of more than 30%, called into question the external validity of these results for the United States. The authors of that trial encouraged replication of their findings in other populations and the performance of a trial with a sample size sufficient “to test the effects of induction on … uncommon adverse neonatal outcomes.” The ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) was designed to test the hypothesis that elective induction of labor at 39 weeks would result in a lower risk of a composite outcome of perinatal death or severe neonatal complications than expectant management among low-risk nulliparous women.