Although doctors for years have advised pregnant women that inducing labor before 41 weeks increased the likelihood of cesarean birth, a sweeping study released recently found that induction at 39 weeks actually reduces the chance of a C-section, while also decreasing other complications for mother and baby.

“In the past, induction at 39 weeks in low-risk women hasn’t been offered — it’s actually been withheld, forbidden, and patients were actively dissuaded from it,” said Dr. William Grobman, a professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine, a Northwestern Medicine physician and the study’s lead author.

The study’s findings, which will be published in the New England Journal of Medicine, may prompt doctors and professional medical societies to dramatically change the way they advise pregnant mothers interested in inducing labor, Grobman said.

“In a world where the foundation for that inclination is no longer true, it seems to make sense to me that we would take a more patient-centered, individualized approach,” he said.

For the study, more than 6,100 women from 41 sites around the country — including Northwestern Medicine — were divided into two groups. One group waited for labor to begin on its own; the other underwent elective induction at 39 weeks of gestation. Study investigators chose 39 weeks because that is when babies have reached full term and have a lower frequency of neonatal complications.

The research found that in the women who were induced at 39 weeks, 19 percent had a C-section delivery, compared with 22 percent of the women who were not induced — a statistically significant difference, researchers said.

In addition, women who were induced at 39 weeks experienced less gestational hypertension than those who were not induced. For mothers who were induced, 9 percent of the group experienced hypertension, compared with 14 percent of the mothers who were not induced.

And while 4 percent of babies born without induction needed respiratory support, only 3 percent of those who were induced required breathing help, the study said.

Christine Escobar, 37, a first-time mother from Chicago’s Roger’s Park neighborhood, said she agreed to participate in the study because she knew that doctors had mixed opinions about the risks of labor induction. As an associate professor of instruction in biological sciences at Northwestern University, Escobar said she liked the idea of contributing to important research, while also helping other mothers have as much information as possible about pregnancy risks and complications.

She and her husband also appreciated the convenience of being able to schedule her induction at 39 weeks, allowing her family from the East Coast to plan travel for the baby’s birth.

“I think it’s empowering,” said Escobar, whose daughter is now 15 months old and was delivered vaginally, without complications. “The more we can learn, the better safety we can bring to babies and moms.”

Grobman, who led the team of more than 20 doctors involved in the research, said they were motivated to do the study because one in four women in the U.S. has labor induced, but up until now, the risks and benefits of such inductions were not well-known.

“How in the world could we, or should we, be doing that as an obstetric community and not be telling people if it helps or hurts?” he said.

While smaller, earlier studies had suggested that labor induction did not increase chances of cesarean delivery, doctors still routinely steered patients away from it, using that unfounded belief, Grobman said.

Grobman said it remains to be seen how the obstetric and gynecological community will change its guidance in light of the new research. But he and other study authors are pleased to be able to arm new mothers with helpful information about their and their babies’ health and safety.

“It was done to provide women information, so they can make choices for their care,” he said.