New Research Shifts Thinking On Pregnancy Dilemma: Induce Labor At 39 Weeks?

(Flickr Creative Commons)
(Flickr Creative Commons)

Jessica Cohen of Quincy, Mass., is nearly 36 weeks pregnant with her first child. And she feels it.

There are the physical challenges: Her back aches and pain shoots across her pelvis. A former dancer, she can only be active for about an hour at a time before she has to take a break. And there is the mental strain of uncertainty, of not knowing when her baby boy will arrive. A late delivery would cut into her husband's time off from work, and it could upend her mother’s plans to travel from Florida for the birth.

Cohen has already told her doctor at Brigham and Women’s Hospital that if the pregnancy continues past her due date, she wants to be induced. That is, she wants her labor to be medically jump-started. But what if she could have an induction sooner, at 39 weeks?

“That would be nice,” she said wistfully.

For many years, the prevailing wisdom for healthy mothers has been to wait. Inducing labor, it was thought, increases a woman’s chances of requiring a Cesarean section, major surgery that could result in complications for mother and baby, and a longer recovery time.

Now, a major study suggests that’s not true.

A large, randomized controlled trial has found that healthy, first-time mothers who choose induction at 39 weeks actually had a lower chance of requiring a C-section than women who continued on into their pregnancies and either delivered spontaneously or with interventions.

To many who work in obstetrics, the results, presented Feb. 1 at the annual meeting of the Society for Maternal-Fetal Medicine, were “an unbelievable, stunning finding,” said Dr. William Grobman, the principal investigator on the trial and professor of obstetrics and gynecology at the Northwestern University Feinberg School of Medicine.

As word spreads, they will surely be surprising to many mothers who worry that induction can lead to C-sections as well. Study authors and others in the field say the trial could prompt a review of obstetric guidelines and a reconsideration of which tools are actually effective at reducing the number of C-sections.

“This is important on a policy level,” said Dr. Uma Reddy, a scientist with the maternal-fetal network at the National Institute of Child Health and Human Development, which funded the study.

Reducing inductions by choice — called elective inductions — has been a central piece of the public health strategy for reducing C-sections, which occur in about one in three deliveries. This study found that inductions may not, in fact, significantly affect the C-section rate.

“To decrease C-section rates,” Reddy said, “we have to look to other things.”

Smaller controlled trials and observational studies have found similar results in recent years. But this study, known as the ARRIVE trial (for “A Randomized Trial of Induction Versus Expectant Management”), was large.

Although it still needs to be fully vetted and published in a peer-reviewed journal, the study included more than 6,000 women at 41 hospitals. It found that, among women who were induced at 39 weeks, 19 percent required a C-section, compared with 22 percent of those whose pregnancies continued in a wait-and-see approach called “expectant management.”

It also found no significant increase in complications for mothers and babies in the induction group. On some measures, both fared better with induction, with just 3 percent of babies requiring respiratory support, for example, compared with 4 percent in the expectant management group.

Dr. Haywood Brown, president of the American College of Obstetricians and Gynecologists, or ACOG, noted the improved outcomes for infants delivered by induction, but said in an email that his organization will wait for the full study results before considering whether to update its guidelines.

ACOG now recommends that induction be used before 41 weeks only when medically necessary — for example, when a mother develops hypertension or her water breaks but labor does not begin.

The trial result, while not a total surprise, “still flies in the face of a lot of what we hold to be true, which is that inductions are interventions and can have bad outcomes,” said Dr. Merielle Stephens, an obstetrician at Cambridge Health Alliance who was not involved in the study.

So, why might the previous thinking on induction have been wrong?

Older studies that set the policy on this topic were poorly designed, Grobman and Reddy said. The older studies compared outcomes from women who chose to have inductions at 39 weeks with women who had gone into labor spontaneously at 39 weeks.

That’s a false comparison, because women cannot choose to go into spontaneous labor — there's no labor switch to flip. The real choice that pregnant women face is between inducing or continuing the pregnancy past that point. And women who continue in pregnancy are likelier to need interventions, including induction or C-section, because the risks of maternal and fetal distress increase as a woman approaches or passes her due date.

“It wasn’t a little flaw,” Grobman said. It was “a fundamental methodological flaw that made the results, in retrospect, essentially useless for clinical decision making. ... That took a while for people to recognize.”

Doctors aren’t likely to start widely recommending that healthy women whose pregnancies are progressing normally begin scheduling inductions at 39 weeks. But the study results, once vetted and published in full, could shift the messaging around inductions.

Some hospitals prohibit elective induction of labor in healthy women who don’t show any cervical changes at 39 weeks, Grobman said. This trial could prompt those policies to be reevaluated.

And it could cause a change in tone, raising the question of whether — and when — elective induction could be considered useful, Reddy said. The risk of stillbirth, for example, increases with gestational age.

“If you deliver a woman at 39 weeks,” she said, “then she’s not going to have a stillbirth at 40 weeks.”

Still, there are good reasons expectant parents may not want an elective induction.

Induction drugs, like pitocin, take time to work. The procedure can require an extended stay in the hospital, and women who are induced are more likely to use an epidural to manage the pain, which comes with its own considerations and possible complications.

Plus, there may be hospital-to-hospital variations in how inductions are practiced, said Dr. Sarah Little, a maternal-fetal medicine specialist at Brigham and Women’s Hospital, who was not involved in the study. If inductions are rushed, she said, they could be more likely to lead to C-sections, a factor that would need to be considered in any change to guidelines.

The study focused on elective inductions, and the results can’t be generalized to inductions that were medically necessary. But, Stephens and Little noted, the study might also provide some comfort to mothers who have medically required inductions, because it suggests that while there may be other factors at play, the induction itself is not likely to push them closer to requiring a C-section.

Cohen said she will stay the course as her due date approaches. She’s been fitted with a back brace to help with the pain, and she’s resting often. Still, while there are few things that are certain at the end of pregnancy, she said if she could know that an induction at 39 weeks wouldn’t increase risks for her or her baby, “I would definitely be on board.”

Chelsea Conaboy is a freelancer who writes often about health care. Find her at and on Twitter @cconaboy.



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