By Amy Norton
WEDNESDAY, Aug. 8, 2018 (HealthDay News) -- Contrary to what doctors have thought, women who opt to have their labor induced in the 39th week of pregnancy do not face a heightened risk of cesarean section, a new clinical trial finds.
In fact, the study showed, those women were less likely to need a C-section than women who let nature take its course. And there was no evidence labor induction carried any added risks for their babies.
The findings, published Aug. 9 in the New England Journal of Medicine, could open up elective labor induction as an option for more women.
Elective inductions -- done for personal reasons rather than medical ones -- have become more common in the United States in recent years, according to the U.S. National Institutes of Health.
However, medical groups have traditionally cautioned against it. The concern is that the practice could increase the need for an emergency C-section or other delivery complications. (When a labor induction fails, a C-section might be necessary.)
"This study provides reassurance that it won't raise the risk of C-section or [newborn] complications," said Dr. Michael Greene, chief of obstetrics at Massachusetts General Hospital, in Boston.
But that doesn't mean elective inductions in the 39th week should be routine, said Greene, who wrote an editorial published with the study.
"I don't foresee a wholesale stampede for this," he said.
Instead, the findings offer better information for women who are interested in the option, according to Greene.
Dr. William Grobman, the lead researcher on the trial, agreed.
Childbirth is "an incredibly personal experience," said Grobman, an obstetrician at Northwestern University, in Chicago.
"Women should have accurate information about the benefits and risks of different options for delivery, so they can make informed choices," he explained.
A full-term pregnancy lasts about 40 weeks, and babies born during the 39th week are considered full-term. But elective induction at that point in pregnancy has been controversial -- except in special circumstances, such as when a woman lives far from a hospital.
However, Grobman said, the concern about inductions driving up C-section rates is based on "flawed studies."
They've compared women who had labor inductions with women who went into spontaneous labor at the same point in pregnancy -- and found that C-sections were more common in the induction group.
But that's not a realistic comparison, Grobman said. "No one is guaranteed to be laboring on the same day they would've had an induction," he noted.
For the study, his team recruited more than 6,100 pregnant women from 41 U.S. hospitals. All were healthy first-time mothers.
The women were randomly assigned to either have an induction during their 39th week, or let nature take its course.
Women and their doctors chose the induction method: In general, it is done either by rupturing the amniotic sac or with hormonal medications that trigger labor.
In the end, the C-section rate was less than 19 percent in the induction group, versus just over 22 percent in the standard-care group, the findings showed.
The researchers also looked at newborn complications -- such as breathing problems, seizures and injuries during delivery. That rate was just over 4 percent in the induction group, and just over 5 percent in the comparison group.
Why would induction reduce the C-section rate?
Greene speculated on one reason: Once a pregnancy has reached full-term, the odds of needing a C-section rise as the days go on. The placenta tends to function less well, Greene explained, and when a woman does go into labor, there can be problems with the baby's oxygen supply. So doctors might end up doing a C-section.
In addition, labor induction may be suggested after a woman goes a week beyond her due date.
"Post-term" births -- beyond week 42 of pregnancy -- carry a slightly higher risk of stillbirth and birth injuries to mother and baby, according to the American College of Obstetricians and Gynecologists.
Women who have labor induced at week 39 face no risk of post-term delivery, Greene said.
Grobman stressed a critical point: If women do consider elective induction, there must be certainty around their due date. This trial included only women who were sure about the date of their last menstrual period, and/or had reliable ultrasound results from the first or second trimesters.
"This should only be an option for women with absolutely reliable information on gestational age," Grobman said.