Public Release: 

Induced labor at 39 weeks reduces cesarean births

Large trial reverses commonly held belief that induction increases cesarean

Northwestern University

  • Elective induction at 39 weeks reduces maternal and newborn complications
  • Newborns have fewer respiratory problems
  • Women report less labor pain, have lower rates of preeclampsia and gestational hypertension
  • Study involved more than 6,100 women

CHICAGO --- For many years, obstetricians counseled women that inducing labor increased the likelihood of a cesarean birth, although there was no solid evidence in clinical trials to support that.

Now, a large national study led by a Northwestern Medicine investigator shows electively inducing labor at 39 weeks actually reduces the rate of cesarean deliveries and decreases maternal and fetal complications.

In the study, women who were assigned to the elective induction group also reported experiencing less pain in labor and a greater sense of control over the labor process than women who were not in the induction group.

The paper will be published Aug. 9 in the New England Journal of Medicine.

"There's a lot of controversy around the consequences of inducing labor. People were convinced that it increased the risk of cesarean delivery, but the reality was actually unknown," said Dr. William Grobman, the Arthur Hale Curtis Professor of Obstetrics and Gynecology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician. "This study provides evidence that inducing labor at 39 weeks actually reduces cesarean delivery."

In the U.S., approximately one-third of women give birth via cesarean delivery, which is associated with an increased risk of infection, hysterectomy, placenta implantation abnormalities in future pregnancies and respiratory illness in infants.

In the study, more than 6,100 women from 41 sites around the country were divided into two groups: one that waited for labor to begin on its own and one that would undergo an elective induction at 39 weeks of gestation.

The investigators chose 39 weeks because that is when babies have reached full term and have a low frequency of neonatal complications.

Among the key results:

  • Lower rates of cesarean delivery among the elective induction group (19 percent) compared to non-induction group (22 percent)
  • Lower rates of preeclampsia and gestational hypertension group (9 percent) compared to the non-induction group (14 percent)
  • Lower rates of respiratory support among newborns in the induction group (3 percent) compared to the non-induction group (4 percent)

The study's data suggest that one cesarean delivery may be avoided for every 28 deliveries among low-risk women giving birth for the first time who plan to undergo elective induction of labor at 39 weeks.

In addition to this large trial, a recent smaller study in Britain found that induction of labor also did not result in an increase of cesarean delivery.

"This new knowledge gives women the autonomy and ability to make more informed choices regarding their pregnancy that better fit with their wishes and beliefs," Grobman said. "Induction at 39 weeks should not be routine for every woman, but it's important to talk with their provider and decide if they want to be induced and when."

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The paper is titled, "Labor Induction versus Expectant Management in Low-Risk Nulliparous Women."

The study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health, grant NCT01990612.

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