(Meredith/CNN) -- Once a mother reaches 39 weeks in her pregnancy journey, she can feel the anticipation and anxiety of what comes next. By that time, physicians will typically go into what's called "expectant management" mode and simply watch and wait until labor ensues.
Yet a new study suggests that inducing labor at 39 weeks can be another viable option for some mothers-to-be, even though it has been shunned in the past.
The large study, published in The New England Journal of Medicine on Wednesday, found that elective induced labor at 39 weeks resulted in a lower likelihood of certain complications and did not result in a greater frequency of adverse outcomes for the baby. Waiting longer to deliver the baby could raise the mother's likelihood of needing to undergo a cesarean section, according to the study.
As it turns out, the study reverses the commonly held belief that induction may increase the chance of delivering by C-section.
Many pregnant women would do anything to avoid a C-section, as the procedure comes with the same risks associated with a major surgery and may also cause problems in future pregnancies. Recovery also takes longer than it would from a vaginal birth.
In the United States, about 31.9 percent of deliveries are by C-section, according to the Centers for Disease Control and Prevention. The World Health Organization has considered the ideal rate for C-sections to be between 10 percent and 15 percent.
"What this study does is it helps us to offer more options to help moms and dads to get to the place where they want to be," said study author Dr. Robert Silver, chairman of the Department of Obstetrics & Gynecology at University of Utah Health and a maternal-fetal medicine physician at Intermountain Healthcare in Salt Lake City.
"So if they really want to be induced because they're uncomfortable or anxious about complications and they really want to maximize their chances of vaginal birth, that's great. If they have no interest in being induced then they don't have to be because the risks are still really low," Silver said.
"This just simply gives us better information to help with that personalized counseling to help patients chose what they want to do," he said. "By no means should people conclude from this study that everybody should be induced at 39 weeks. It simply means that it is a reasonable option for people who chose to."
The study was conducted as a randomized, controlled trial that involved 6,106 pregnant women across 41 US hospitals that participate in the maternal-fetal medicine units network of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
The women, who were all first-time moms-to-be and had low-risk pregnancies, were separated into two groups: 3,062 were in a group that would be induced at 39 weeks and 3,044 were in an expectant-management group that would wait until spontaneous labor.
While the outcomes for the infants were generally similar in both groups, the researchers found that fewer women, 18.6 percent, underwent C-section deliveries in the induction group compared with 22.2 percent in the expectant management group.
The data suggest that one C-section may be avoided for every 28 deliveries among low-risk, first-time expecting mothers who plan to undergo elective induction of labor at 39 weeks, the researchers noted in their study.
Also, fewer women, 9.1 percent, had pregnancy-related hypertensive disorders in the induction group compared with 14.1 percent in the expectant management group, the researchers found, and women in the induction group reported less pain and more perceived control during childbirth.
Women in the induction group spent more time in the labor and delivery unit, but the length of their postpartum hospital stay was shorter, the researchers found.
Based on their findings, the researchers wrote in the study, "labor induction is probably not associated with a higher risk of adverse perinatal outcomes than expectant management, and it may be associated with as much as a 36 percent lower risk than expectant management."
The study had some limitations, including that the women knew which group they were assigned to in the study -- it was not possible to conduct a blind trial -- and only involved low-risk, first-time pregnancies. More research is needed to determine how the findings would change among higher risk pregnancies.
More research is needed also to determine which option for expectant mothers is more cost-effective, and how much of a dent an elective induced labor could put in a family's wallet.
"The truth is we haven't done cost analysis yet and we're currently working on that," Silver said. "We have the data collected from this study but we haven't done the analyses and so we look forward to that as being an important part of this equation."
The new study findings likely will drive a change in practice, said Dr. Errol Norwitz, chairman of the Department of Obstetrics and Gynecology and chief scientific officer at Tufts Medical Center in Boston, who was not involved in the study.
"I think the way we're going to communicate with people now is to say, if you chose to have an induction of labor after 39 weeks, it turns out it doesn't make any difference in the outcome for the fetus, it doesn't increase your risk of cesarean delivery, and the data suggest that it actually decreases the risk of cesarean," Norwitz said.
"So I think the way we counsel patients, the way we communicate to patients, is going to change and it's data-driven," he said. "Our job as physicians is not to tell patients what to do, but to counsel and provide the data so that they can make the best decision for them, and they're ultimately driving the decision making."
Before the new study, women who would ask about undergoing a labor induction at 39 weeks sometimes would be advised to wait until they reached at least 41 weeks in their pregnancy, said Dr. Cynthia Gyamfi-Bannerman, an obstetrician-gynecologist at New York-Presbyterian/Columbia University Medical Center in New York who was not involved in the study. Columbia was a location for the study though.
"So that used to be the answer because we've never really been a fan -- at least I've never been a fan -- of an elective induction without some type of indication. But what this study has shown us is that 39 weeks is kind of optimal for the baby," she said.
Risks associated with a post-term or prolonged pregnancy -- a pregnancy that continues for longer than 42 weeks -- include placental problems, infections in the womb, and unexpected complications, such as preeclampsia, a complication characterized by high blood pressure.
"Certainly, it's not that all women who reach 39 weeks are going to be induced," Gyamfi-Bannerman said. "The message here is that low-risk women can have a conversation with your doctor about what to do once you reach 39 weeks and, as with everything, discuss the risk and benefits and then make an informed decision on what you would like to do."
While the new study only included women with low-risk, first-time pregnancies, there are populations of women with certain risk factors who possibly could benefit from labor induction at 39 weeks, said Dr. Haywood Brown, the immediate past president of the American College of Obstetricians and Gynecologists, who was not involved in the study.
"For instance, we know that women who are obese and particularly black women have a higher risk of stillbirth at term. So is this a group that should be induced anyway at 39 weeks? My answer is yes," said Brown, who was recently appointed vice president for diversity, inclusion and equal opportunity at the University of South Florida System, associate dean for diversity at the university's Morsani College of Medicine in Tampa.
"We also know that there are certain older women, women who are older than 40, who may have a slightly higher risk of having a stillbirth at term. So is this a group that would automatically fall into that category of women who should be induced at 39 weeks? I happen to believe that's the case," Brown said.
Of course, he added, such labor inductions would have to be a part of "shared decision making" between a mother-to-be and her physician.
"Overall, I think it is reasonable to conclude that if you are having your first baby, and your pregnancy is uncomplicated and your fetus is in a vertex -- or head-first -- presentation, then elective induction of labor at 39 weeks is potentially associated with about a 20 percent reduction in the occurrence of adverse infant outcomes and cesarean delivery," said Dr. Charles Lockwood, senior vice president of University of South Florida Health and dean of the Morsani College of Medicine, who was not involved in the new study.
"Other epidemiological data on rates of stillbirth versus complications of later preterm or early term birth also suggest 39 weeks is the optimal time of delivery," Lockwood said.
He added that for women who desire a non-medical and more natural birthing experience, those "modest clinical benefits" may not be "sufficient to warrant" an induced labor, and that's OK. The new study simply suggests that induction can be an option, while the ultimate birthing decision remains with the family.
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