Induced labor at 39 weeks may reduce likelihood of C-section, new study suggests

Healthy first-time mothers who were randomly assigned to labor induction in the 39th week of pregnancy were less likely to undergo a cesarean section than those who were assigned to wait for labor to begin naturally, finds a new study funded by the National Institutes of Health (NIH). Women assigned to labor induction at 39 weeks were less likely to experience pregnancy-associated hypertension and their babies were less likely to require respiratory support.

The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) funded the study to determine the risks and benefits of elective induction at 39 weeks. The Biostatistics Center based at George Washington University’s Milken Institute School of Public Health (GW Milken Institute SPH) served as the data coordinating center. The Biostatistics Center provided leadership in and had primary responsibility for the design, execution, coordination, data management, and analysis of the trial, among other responsibilities. 

Prior to the study, doctors were concerned that inducing labor at 39 weeks would increase the likelihood of needing a cesarean section. Although safe, women take longer to recover from a cesarean section, compared with vaginal birth, and the surgery may increase the risk of problems with vaginal birth in future pregnancies.

“In healthy first-time moms, induction of labor at 39 weeks appears to be safe for the baby and may even benefit the mother by reducing her chances of cesarean delivery or developing high blood pressure late in her pregnancy,” said Madeline Murguia Rice, Ph.D., an Associate Research Professor of Epidemiology and Biostatistics at Milken Institute SPH, and Co-Investigator of the NICHD Maternal-Fetal Medicine Units Network Data Coordinating Center. “This information can be useful when women and their care providers are discussing the option of induction of labor at 39 weeks as an alternative to waiting for labor to begin naturally.”

The study followed over 6,000 pregnant women at 41 hospitals in the NICHD Maternal-Fetal Medicine Units Network. About half of the women were randomly assigned to have labor induced between 39 weeks, 0 days and 39 weeks, 4 days while the rest were randomly assigned to wait until at least 40 weeks and 5 days for labor to occur naturally or have a medical reason to deliver.

The researchers compared births between the two groups to see if there were any birth complications, such as newborn death or birth injury. The primary outcome of death or severe complications in the newborn 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. There was no increased risk of maternal complications among those assigned to labor induction, but the group did have a significantly lower likelihood of cesarean delivery than the other group. The researchers estimate that one cesarean section could be avoided for every 28 low-risk, first-time mothers undergoing induced labor at 39 weeks.

The study’s results were published in detail in the August 9 issue of the New England Journal of Medicine.