DALLAS – Elective inductions at 39 weeks’ gestation were safe for the newborn and conferred dual benefits upon first-time mothers, reducing the risk of cesarean delivery by 16% and pregnancy-related hypertensive disorder by 36%, compared with women managed expectantly.
Infants delivered by elective inductions were smaller than those born to expectantly managed women and experienced a 29% reduction in the need for respiratory support at birth, William A. Grobman, MD, reported at the meeting, sponsored by the Society for Maternal-Fetal Medicine. They were no more likely than infants in the comparator group to experience dangerous perinatal outcomes, including low Apgar scores, meconium inhalation, hypoxia, or birth trauma, said Dr. Grobman, professor of obstetrics and gynecology at Northwestern University, Chicago.
Michele G. Sullivan/Frontline Medical News
Dr. William A. Grobman
The new data, however, may set a new standard by which to make this decision, Dr. Grobman said.
“I will leave it up to the professional organizations to determine the final outcome of these data, but it’s important to understand that the Choosing Wisely recommendation was based on observational data that essentially used an incorrect clinical comparator” of spontaneous labor, he said. The large study that Dr. Grobman and his colleagues conducted used expectant management (EM) as the comparator, allowing women to continue up to 42 weeks’ gestation. Using this comparator, he said, “Our data are largely with almost every observational study” and with a recently published randomized controlled trial by Kate F. Walker, a clinical research fellow at the University of Nottingham (England).
That study determined that labor induction between 39 weeks and 39 weeks, 6 days, in women older than 35 years had no significant effect on the rate of cesarean section and no adverse short-term effects on maternal or neonatal outcomes.
Dr. Grobman conducted his randomized trial at 41 hospitals in the National Institutes of Health’s Maternal-Fetal Medicine Units Network.
It randomized 6,106 healthy, nulliparous women to either elective induction from 39 weeks to 39 weeks, 4 days, or to EM. These women were asked to forgo elective delivery before 40 weeks, 5 days, but to be delivered by 42 weeks, 2 days.
The primary perinatal outcome was a composite endpoint that included fetal or neonatal death; respiratory support in the first 72 hours; 5-minute Apgar of 3 or lower; hypoxic ischemic encephalopathy; seizure; infection; meconium aspiration syndrome; birth trauma; intracranial or subgaleal hemorrhage; and hypotension requiring vasopressors.
The primary maternal outcome was a composite of cesarean delivery; hypertensive disorder of pregnancy; postpartum hemorrhage; chorioamnionitis; postpartum infection; labor pain; and the Labour Agentry Scale, a midwife-created measure of a laboring woman’s perception of her birth experience.
Women were a mean of 23.5 years old; about 44% of each group was privately insured. Prior pregnancy loss was more common among those randomized to EM (25.6% vs. 22.8%). Just over half were obese, with a body mass index of at least 30 kg/m2. Most (about 63%) had an unfavorable cervix, with a Bishop score of less than 5. The trial specified no particular induction regimen, Dr. Grobman said. “There were a variety of ripening agents and oxytocin regimens used.”
Infants in the elective induction group were born significantly earlier than were those in the EM group (39.3 vs. 40 weeks) and weighed significantly less (3,300 g vs. 3,380 g). Induction was safe for the newborn, with the primary endpoint occurring in 4.4%, compared with 5.4% of those in the EM group – not significantly different.
When investigators examined each outcome in the perinatal composite individually, only one – early respiratory support – was significantly different from the EM group. Infants in the induction group were 29% less likely to need respiratory support in the first 72 hours (3% vs. 4.2%; relative risk, 0.71). The rate of cesarean delivery also was significantly less among the induction group (18.6% vs. 22.2%; RR, 0.84).
None of these outcomes changed when the investigators controlled for race/ethnicity, Bishop score of less than 5, body mass index of 30 kg/m2 or more, or advanced maternal age.
Induction also was safe for mothers, and conferred a significant 36% reduction in the risk of pregnancy-related hypertensive disorders (9.1% vs. 14.1%; RR, 0.64). All other maternal outcomes were similar between the two groups.
The Agentry scale results also showed that women who were induced felt they were more in control of their birth experience, both at delivery and at 6 weeks’ postpartum. They also rated their worst labor pain and overall labor pain as significantly less than did women in the EM group.
“Our result suggest that policies directed toward avoidance of elective labor induction in nulliparous women would be unlikely to reduce the rate of cesarean section on a population level,” Dr. Grobman said. “To the contrary, our data show that, for every 28 nulliparous women to undergo elective induction at 39 weeks, one cesarean section would be avoided. Additionally, the number needed to treat to prevent one case of neonatal respiratory support is 83, and to prevent one case of hypertensive disease of pregnancy, 20. Our results should provide information useful to women as they consider their options, and can be incorporated into shared decision-making discussions with the provider.”
The study was sponsored by the National Institutes of Health. Dr. Grobman had no financial disclosures.
SOURCE: Grobman W. Am J Obstet Gynecol. 2018 Jan;218:S601.