Nulliparous pregnant women with an unfavorable cervix who were induced after 39 weeks’ gestation were more likely to have a cesarean delivery than were women undergoing expectant management, but the ceserean rate was not doubled, according to a new study.
The randomized clinical trial of 162 pregnant women was powered only to detect a twofold difference in cesearean rates since that rate has been cited in older observational studies and some guidelines as evidence against elective induction, according to Dr. Nathaniel R. Miller of the Carl R. Darnall Army Medical Center in Fort Hood, Tex., and his associates.
“Clearly, less-modest increases in the cesarean delivery rate may be clinically important, and future studies should be powered to detect smaller differences in the cesarean delivery rate between induction and expectant management,” the researchers wrote.
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Researchers randomized 162 nulliparous pregnant women to elective induction of labor or expectant management when they were between 38 weeks 0 days and 38 weeks 6 days of gestation. The women were at least 18 years old with a singleton pregnancy with cephalic presentation, and a Bishop score no higher than 5. Inductions occurred within a week of enrollment, which ran from March 2010 to February 2014, but no women were induced before 39 weeks 0 days (Obstet Gynecol. 2015;126:1258-64).
Cesarean delivery was indicated if at least one of the following was present: nonreassuring fetal status (persistent category II or III); active phase arrest of dilation; arrest of descent in the second stage of labor; or failed induction of labor.
Among the 82 women assigned to induction, 3 did not receive the intervention, 2% were admitted in spontaneous labor, and 30.5% had a cesarean delivery. Among 80 women randomized to expectant management, after excluding 1 lost to follow-up, 44% were admitted in spontaneous labor and 17.7% had a cesarean delivery.
The risk of cesarean delivery between the groups, however, was not statistically significant (relative risk, 1.72; 95% confidence interval 0.96-3.06). Neither postpartum length of stay nor indications for cesarean delivery significantly differed between the two groups, though maternal total hospital length of stay was 10 hours longer in the induction group and inductions for hypertensive disorders were greater in the expectant management group.
“The consistent message from the expanding literature on this topic is that there are and will continue to be important trade-offs to weigh in the balance, especially when it comes to discussing the risk of cesarean delivery with induction in this seemingly highest-risk population of nulliparous women with an unfavorable cervix,” the resarchers wrote.
Additionally, the study defined active phase arrest of dilation as “2 hours of no cervical change once 4 cm or more dilation had been reached after rupture of membranes,” rather than the 4 hours recommended by guidelines for prevention of the first cesarean delivery, published in November 2012 by the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Society for Maternal Fetal Medicine, and the American College of Obstetricians and Gynecologists. Since the most common indication for cesarean delivery in the induction group was arrest of dilation, use of the 4-hour criteria “would have resulted in a reduction in the cesarean delivery rate for the induction of labor arm to 20% and the expectant management arm to 15%,” the researchers noted.
The researchers reported having no financial disclosures.