Cesarean Rates Lower With Induced Labor vs Expectant Management

Nancy A. Melville

February 12, 2018

DALLAS — Elective induction of labor among low-risk women at 39 weeks' gestation is associated with a reduced rate of cesarean delivery compared with expectant management, results of a large, randomized trial show. Other maternal and infant outcome measures also improved, researchers reported in a late-breaking abstract session here at the Society for Maternal-Fetal Medicine's 38th Annual Pregnancy Meeting.

"Our results suggest that policies directed toward avoidance of elected labor induction in nulliparous women would be unlikely to reduce the rate of cesarean delivery on a population level," said first author William Grobman, MD, from the Northwestern University Feinberg School of Medicine in Chicago, Illinois.

The multicenter ARRIVE trial, conducted at 41 hospitals in the National Institutes of Health's Maternal-Fetal Medicine Units Network, is the largest randomized trial on the issue to date, involving more than 6100 patients at 41 centers.

Overall, the cesarean delivery rate was 18.6% among the 3062 women randomly assigned to elective induction at 39 weeks compared with 22.2% among 3044 women in the expectant management group (RR, 0.84).

In addition, maternal adverse outcomes, including preeclampsia and gestational hypertension, were significantly lower in the induced labor group, and neonates in the induced labor group were nearly 30% less likely to experience respiratory morbidity. Other outcomes were similar between the two groups.

Guidelines from the American College of Obstetricians and Gynecologists currently say that elective induction may be considered much later than 39 weeks — at 41 weeks — and should be performed at 42 weeks. However, mounting evidence consistent with the new findings is pushing the field toward greater acceptance of elective induction at 39 weeks.

As reported by Medscape Medical News, a planned debate on the issue at the 2016 American College of Obstetricians and Gynecologists meeting in fact unexpectedly resulted in both sides arguing strongly on the pro side of induction at 39 weeks in low-risk women.

Key concerns with induced labor between 39 and 40 weeks have largely focused on nulliparous women with an unfavorable cervix and the concern of adverse maternal outcomes and increases in cesarean delivery, which carries a host of risks including infection, hysterectomy, and respiratory illness in infants.

However, Grobman said the numbers needed to treat that can be derived from the new study suggest the risk is not increased in low-risk women.

"To the contrary, our data show that for every 28 nulliparous women who undergo induction of labor at 39 weeks, one cesarean would be avoided," he said.

"Moreover, the number needed to induce to prevent one case of neonatal respiratory support is 83, and the number [needed] to prevent one case of hypertensive disorder of pregnancy is 20."

Findings Broadly Generalizable, Researchers Say

In the study, conducted from March 2014 to August 2017, researchers randomly assigned 6106 low-risk women between 38 weeks and 0 days and 38 weeks and 6 days of gestation to have either elective induction between 39 weeks and 0 days to 39 weeks and 4 days or expectant management, forgoing elective delivery before 40 weeks and 5 days and delivery no later than 42 weeks and 2 days.

Of those women, 94% in the induced labor group and 95% in the expectant management group adhered to the protocol of their assigned group.

Delivery was significantly earlier among those in the induced labor group (39.3 vs 40.0 weeks; P < .001), and birthweight was lower compared with in the expectant management group (3300 vs 3380 g; P < .001).

The primary outcome, which was a composite of adverse perinatal events, was similar between the two groups, at 4.3% in the elective induction group and 5.4% in the expectant management group (RR, 0.80; P = .049 [P < .046 was determined to indicate statistical significance]). Adverse perinatal events included in the composite included perinatal death, an Apgar score of 3 or lower at 5 minutes, hypoxic ischemic encephalopathy, seizures, infection, meconium aspiration syndrome, birth trauma, intracranial or subgaleal hemorrhage, or hypotension requiring pressor support.

A notable difference in outcomes included the need for neonatal respiratory support, which was lower in the induced labor group (3.0% vs 4.2%; RR, 0.71, 95% confidence interval, 0.55 - 0.93).

In addition, the rate of hypertension disorder in pregnancy was also lower in the induced labor group (9.1%) vs in the expectant management group (14.1%; RR, 0.64; 95% confidence interval, 0.56 - 0.74).

Although women in the induced labor group had a slightly lower rate of previous pregnancy loss than those in the expected management group, the lower cesarean rate observed in this group did not change after adjustment for the previous pregnancy loss.

Outcomes in patient-reported outcomes, including the labor agentry score after delivery and at 6 weeks, which is indicative of perceived personal control during pregnancy and childbirth, were higher for the induced labor group (P < .001 and P = .01, respectively), and measures of worst labor pain and overall labor pain were also more favorable with induced labor (both P < .001).

There were no significant differences between the groups in terms of race, maternal age, body mass index, or modified Bishop score either in the composite measures of the primary perinatal outcome or in relation to cesarean delivery.

"In this randomized trial induction of labor of nulliparous women at 39 weeks of gestation, induction resulted in no difference in the primary perinatal composite outcome," Grobman said.

"Conversely, there was, in the induction group, a significantly lower frequency of cesarean delivery, neonatal respiratory support, and hypertensive disorder of pregnancy, as well as lower perceived pain in labor [and] greater perceived control during childbirth process."

He noted that previous observational studies that have shown a link between elective induction and cesarean delivery have been flawed in commonly using spontaneous labor as the clinical comparator.

"Such comparison provides little insight into clinical outcomes, as spontaneous labor is not a certain alternative to induction," he said.

"Instead, most observational studies using a clinically relevant comparator of expectant management have not replicated this association."

He pointed out a previous randomized study published in the New England Journal of Medicine in 2016. The study, which enrolled 619 women aged 35 years and older, used the comparator of expectant management and showed no significant differences in the percentage of those who underwent a cesarean section or in adverse maternal or neonatal outcomes compared with elective labor induction at 39 weeks, he noted.

By expanding the research to 41 centers, the new study casts a broader net, suggesting the findings may represent varying protocols.

"No single induction protocol was mandated, as such the study's generalizability should be enhanced," Grobman said.

"Our results should provide information to women either way, as they consider their options to discuss with their providers," he added.

Specific Protocols Needed

In commenting on the study, Elliott K. Main, MD, medical director of the California Maternal Quality Care Collaborative at Stanford University, Palo Alto, said it should be noted that all the centers in the trial were university hospitals, making adherence to labor guidelines more uniform.

"Induction is [a] long, complex, multistep process that is performed in many different ways by different providers and different labor floors," Main told Medscape Medical News.

"Standardization of labor management is critically important for achieving good outcomes," he added.

The findings on neonatal outcomes are generally consistent with previous studies that have not shown improved overall neonatal outcomes with induction. He said that the exception of the reduced need for respiratory support in the induction group likely reflects later deliveries in the expectant management group.

"The higher rate of the submeasure of respiratory support in the expectant management group is likely related to allowing mothers to go as far as 42 weeks and 2 days," Main said. "As pregnancies go beyond 41 weeks, the rates of meconium skyrocket."

He underscored that adherence to specific protocols would be critical in the safe use of elective labor induction.

"This is a well-done study, but widespread adoption of elective induction should not occur unless it is also accompanied by strict labor management guidelines including the formal definition of failed induction."

The study is being submitted for publication, and the Society for Maternal-Fetal Medicine will review the peer-reviewed manuscript in evaluating possible updates in recommendations on elective labor induction, Alfred Z. Abuhamad, MD, immediate past president of the society, told Medscape Medical News.

"I think, based on the evidence we see from the manuscript, we will have to make some recommendations in the practice of medicine," said Dr Abuhamad, who is professor and chairman for the Department of Obstetrics and Gynecology and Associate Dean for Clinical Affairs at Eastern Virginia Medical School, Norfolk.

"It's hard to predict what we will see, but based on the data I've seen from this study so far, my opinion is that elective induction of labor should be an option for women at 39 weeks," he added.

"I think the data is strong and will be impactful to the practice of medicine."

The study received support from the National Institutes of Health and the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Grobman, Main, and Abuhamad have disclosed no relevant financial relationships.

Society for Maternal-Fetal Medicine's 38th Annual Pregnancy Meeting: Abstract LB01. Presented February 1, 2018.

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