Inducing labour at 39 weeks in healthy pregnant women reduces the need for cesarean section and is at least as safe for baby and mother as waiting for spontaneous labour. Opting to induce could also reduce the risk of preeclampsia in mothers and the need for respiratory support after delivery in newborns. These mothers were no more likely to experience stillbirth, newborn death or other severe complications, compared to infants born to uninduced women. The findings are published in the New England Journal of Medicine.
William A. Grobman, the Department of Obstetrics and Gynecology, Northwestern University, Chicago, and colleagues conducted the study to determine the perinatal and maternal consequences of induction of labor at 39 weeks among low-risk nulliparous women.
“This doesn’t mean that everyone should be induced at 39 weeks,” says the study’s co-author Robert Silver, chair of Obstetrics & Gynecology at the University of Utah Health. “Electing to induce labor is a reasonable option that may give the best chance for vaginal delivery and improve outcomes.”
The rate of babies being delivered by C-section is steadily increasing. Unnecessary cesarean deliveries in healthy first-time mothers is a point of concern and account for about 80% of the deliveries. Although the procedure is generally safe, the major surgery increases the risk for complications to both mother and baby, and to future pregnancies. Women who deliver by C-section once are more likely to continue delivering that way, increasing the likelihood of high-risk complications such as placenta accreta.
For years, health care providers had been taught to avoid inducing labor in healthy, first-time mothers based on the belief that inducing increases the chance for C-section births. However, recent results from small, observational studies indicated that this may not necessarily be the case.
The study was conducted on the first-time mothers enrolled in the randomized ARRIVE clinical trial. More than 1,200 women were at the Utah MFMUN, consisting of University Hospital and Intermountain Medical Center, the largest enrolling site in the trial.
ARRIVE was a prospective trial designed to test this premise by examining outcomes from two groups of healthy, first-time mothers. One group elected to induce labor at 39 weeks when the baby is full term and it is considered safe for mothers to give birth. The other group took part in expectant management or “watchful waiting,” the routine practice of waiting for spontaneous labor but undergoing active intervention should a medical need arise.
A total of 3062 women were assigned to labor induction, and 3044 were assigned to expectant management. The primary outcome was a composite of perinatal death or severe neonatal complications; the principal secondary outcome was cesarean delivery.
- A composite score measuring several health indicators in newborns — including death, seizures, hemorrhage, and trauma — occurred in 4.3% of neonates in the induction group and in 5.4% in the expectant management group.
- The frequency of cesarean delivery was significantly lower in the induction group than in the expectant management group (18.6% vs. 22.2%).
- Women who chose to induce at 39 weeks delivered nearly one week earlier than women who waited for spontaneous labor.
- Inducing labor was linked to significant improvement in two specific outcomes: women were less likely to develop preeclampsia (9 vs. 14 percent), and rates of respiratory distress decreased in newborns.
Based on these data, the researchers estimate that inducing labor at 39 weeks could eliminate the need for 1 C-section for every 28 deliveries.
Silver says that the placenta tends not to function as well later in pregnancy, possibly explaining why mothers and babies who deliver earlier may fare better.
“Induction of labor at 39 weeks in low-risk nulliparous women did not result in a significantly lower frequency of a composite adverse perinatal outcome, but it did result in a significantly lower frequency of cesarean delivery,” concluded the authors.
For more information log on to 10.1056/NEJMoa1800566
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