Induced Labor At 39 Weeks Reduces Risk of C-section, Study Finds

by NCN Health And Science Team Posted on August 9th, 2018

Washington, D.C., USA : Healthy first-time mothers whose labor was induced in the 39th week of pregnancy were less likely to deliver by cesarean section, compared to those who waited for labor to begin naturally, according to a study funded by the National Institutes of Health. Elective induction at 39 weeks is also linked to lower risk of maternal high blood pressure disorders.

Researchers also found that infants born to women induced at 39 weeks were no more likely to experience stillbirth, newborn death or other severe complications, compared to infants born to uninduced women. The results of the study titled “Labor Induction versus Expectant Management in Low-Risk Nulliparous Women” was published in the New England Journal of Medicine.

“Prior to this study, there was concern that induction of labor would increase the chance of cesarean delivery,” said study author Uma M. Reddy, M.D., of the Pregnancy and Perinatology Branch of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “Our analysis suggests that elective induction at 39 weeks is associated with a lower rate of cesarean delivery and does not increase the risk of major complications for newborns.”

Although cesarean delivery is safe for mother and baby, it is major surgery and does carry risks. It takes longer to recover from a C-section, compared to vaginal birth, and the surgery may increase the risk of problems with vaginal birth in future pregnancies.

Elective induction — labor induced when there is no medical need to do so — before 39 weeks (link is external) is known to pose health risks for newborns. However, elective induction at 39 weeks, or one week before the due date, has become more common in recent years, said Dr. Reddy.

NICHD funded the current study to determine the potential risks and benefits of elective induction at 39 weeks, compared to expectant management, or waiting for labor to begin naturally, with health care practitioners intervening if problems occur.

The study enrolled more than 6,000 pregnant women at 41 hospitals participating in the NICHD-supported Maternal-Fetal Medicine Units Network. Roughly half of the women were assigned at random to have their labor induced in the 39th week of pregnancy; the remaining women received expectant management.

The researchers compared births between the two groups in terms of a primary outcome, a composite measure that included death of the baby during or after birth; the newborn’s need for respiratory support; seizure, infection, birth trauma (injury) or hemorrhage; and other birth complications.

The primary outcome occurred in 4.3 percent of the induced labor group and 5.4 percent of the expectant management group, a difference that was not statistically significant. However, the proportion of cesarean delivery was significantly lower for the induced group (18.6 percent), compared to the other group (22.2 percent). Similarly, the rate of blood pressure disorders of pregnancy was significantly lower in women who were induced (9.1 percent), compared to the other group (14.1 percent).

The researchers estimate that one cesarean delivery could be avoided for every 28 low-risk, first-time mothers undergoing elective induction at 39 weeks.

“If you deliver the baby before 39 weeks, then there’s an increased risk of medical problems,” said study co-author Dr. Robert Silver, chairman of obstetrics and gynecology at University of Utah Health. “Once you get to 39 weeks, the baby’s developed enough that there’s really no benefit” to holding off.

Minorities who participated in the study still experienced more adverse outcomes than their white counterparts overall. But those in the induction group also benefited from the elective induction, Silver said.

“There was reduced risk of cesarean and preeclampsia regardless of race or ethnicity, and there was reduction of pulmonary disease in the baby regardless of race and ethnicity,” he said.

Induction isn’t right for every woman, the researchers say. Those who desire a more holistic approach should still plan for that, as long as their obstetrician deems it safe.

“People shouldn’t be afraid to go past 39 weeks,” Silver said. “This doesn’t mean it’s a better option and that everyone should be induced at 39 weeks. It simply means you aren’t going to cause harm.”

The trial was the largest of its kind. The findings received a cautious endorsement from the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine.

“It is reasonable for obstetric care providers to offer an induction of labor to low-risk women after discussing the options thoroughly, as shared decision making is a critical element,” the groups said in a statement, adding that this only applies to women with no complications who are delivering their first babies and have had an ultrasound early in pregnancy to confirm their due date.

The new research comes at a crucial time for maternal care. Each year in America, about 700 women die as a result of pregnancy or delivery issues — while 50,000 experience severe complications, according to the Centers for Disease Control and Prevention, CDC.

The problems are particularly magnified for women of color. Black women are three to four times more likely than white women to die from pregnancy-related causes nationwide, the CDC says.

About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): NICHD conducts and supports research in the United States and throughout the world on fetal, infant and child development; maternal, child and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit

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