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Elective induction of labor at 39 (vs 41) weeks: Caveats and considerations

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“39 weeks and out” concluded Errol Norwitz, MD, PhD, during a debate at the 2016 ACOG Annual Clinical and Scientific Meeting. His co-debater Charles Lockwood, MD, agreed. Here, a look at their conclusions, and what could be important to keep in mind.



Tasked with tackling the literature on the subject and debating the question of whether or not it is best to electively induce labor in women with low-risk pregnancies at 39 weeks (vs at 41 weeks after expectant management), Errol Norwitz, MD, PhD, Chairman of the Department of Obstetrics and Gynecology and Professor at Tufts University School of Medicine in Boston, Massachusetts, and Charles Lockwood, MD, Senior Vice President at the University of South Florida (USF) and Dean of the USF Health Morsani College of Medicine in Tampa came to the same conclusion: Elective induction of labor (eIOL) at 39 weeks is superior to expectant management when it comes to fetal outcomes.

In addition, they both agreed that complication rates to the mother (ie, number of cesarean deliveries [CDs]) would not be increased, and possibly even reduced, with eIOL at 39 weeks versus 41 weeks. Dr. Norwitz postulated that, with IOL there is no increase in CD rate in multiparous women and nulliparous women with a favorable cervical exam but that there likely could be an increase in the CD rate for nulliparous women with an unfavorable cervical exam.

The finding that eIOL at 39 weeks is better than at 41 weeks for the infant is likely due to a bigger baby size past 39 weeks (with more traumatic deliveries) and higher rates of postmaturity complications, said Dr. Lockwood. And for the mother, eIOL at 39 weeks can reduce risks—of preeclampsia, abruption, sepsis, and others—the presenters pointed out.

Arriving at their conclusions: The dataDr. Norwitz explained the challenge before them in this unusual “debate.” “In ObGyn we all read the same literature but we often come away with very different takes as to what the implications are and how we incorporate this into our management algorithms. Instead of taking a pro/con approach, with one assigned to ‘yes’ and the other assigned to ‘no,’ and selectively picking out the literature to support our positions, what we did was we each went away, read the literature, synthesized it, and tried to answer this question for ourselves.”

Dr. Norwitz, who is widely published and known for his research on the causes and prevention of preeclampsia and preterm labor, examined and presented the published literature for benefit and harms to the fetus and mother in continuing pregnancy past 39 weeks.

Dr. Lockwood also examined the literature, including a large population cohort of about 1.27 million women that examined CD rates, perinatal mortality, and neonatal and maternal outcomes of eIOL at 39 weeks versus expectant management.1 He presented, however, that the best evidence to compare the question at hand would be a randomized clinical trial comparing specifically eIOL at 39 weeks versus expectant management, with IOL at 41 weeks. To be powered to detect a difference in perinatal and maternal mortality, this trial would need to include 2.2 to 12.6 million women, he maintained. “When empirical evidence doesn’t exist, the only alternative is some kind of other modeling,” he said. Therefore, he and a team of researchers conducted a Monte Carlo microsimulation modeling decision analysis, taking into account “all outcomes and all preferences that we possibly could cull from the literature.”

Which women actually could benefit from eIOL at 39 weeks?Women with high-risk pregnancies were not included in this debate or considered. Dr. Norwitz clearly defined his case patient at the outset as a 22-year-old G1 at 39 0/7 weeks who has had an uncomplicated pregnancy but is now complaining of decreased fetal movement and tells you that she is worried because her sister lost her baby at 40 weeks to stillbirth. She specifically asks, “Doctor, why can’t you induce my labor now?”

What counseling a patient about the risks/benefits of eIOL at 39 weeks would requireTwo fundamentals would need to be ensured. The first: precise gestational dating. Dr. Norwitz pointed out that menstrual history can be inaccurate, especially in women with irregular cycles, who are taking hormonal contraception, or who have intermenstrual bleeding. “Early dating ultrasound is the best way to date pregnancies and probably should be done routinely,” although it is not currently standard of care in the United States, he said.

The second fundamental: a true induction of labor process, not one that involves “stopping at 5 PM,” said Dr. Lockwood.

“Although Dr. Lockwood’s 5-PM statement was made tongue-in-cheek,” said Dr. Norwitz after the debate, “he certainly was implying that a genuine effort should be made to effect a vaginal delivery—that is, giving the most effective cervical ripening agents, allowing enough time to pass, and defining clearly the criteria for failed IOL. You shouldn’t just throw the towel in at 5 PM because you want to go home.”

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