Elective induction of labor in first-time mothers with an unfavorable cervix increased the rate of cesarean deliveries compared with women who received expectant management in a randomized clinical trial, but the differences were not statistically significant.
Although retrospective studies comparing elective induction with expectant management do not show an increased risk for cesarean delivery, and in fact a body of literature suggests elective induction may reduce cesarean deliveries by up to 20%, these findings may not be reflective of special populations.
Patients with an unfavorable cervix “have largely been excluded from prospective studies on this subject,” Nathaniel R. Miller, MD, from the Carl R. Darnall Army Medical Center in Fort Hood, Texas, and colleagues write in their article, published in the December issue of Obstetrics & Gynecology. They note that the nonrandomized data suggest this population may have a higher risk for cesarean delivery when electively induced.
To investigate the association, the researchers randomly assigned 162 nulliparous women at 39 weeks of gestation with a Bishop score 5 or less to elective induction or expectant management. Three women in the induction group changed their minds, and one woman in the expectant management group was lost to follow-up. Inductions occurred within a week of enrollment, which ran from March 2010 to February 2014.
Indications for cesarean delivery included 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.
Of the 79 women in the labor induction group, 25 (30.5%) had a cesarean delivery compared with 14 (17.7%) of the 79 women in the expectant management group (relative risk, 1.72; 95% confidence interval, 0.97 – 3.06; P = 087). Admissions for spontaneous labor occurred in 2% of the intervention group and 44% of the control group.
The most common indication for cesarean delivery in the induction group was arrest of dilation. However, the study defined active phase arrest of dilation as 2 hours with no cervical change once 4 cm or more dilation had been achieved after rupture of membranes, which is 2 hours less than that recommended in national guidelines. If the study used the more liberal 4-hour criteria, the cesarean delivery rate for the induction of labor group would have been reduced to 20% and 15%, respectively, for the intervention and control groups, the authors explain.
There was no statistically significant between-group difference in the risk for cesarean delivery, nor were there significant between-group differences in postpartum length of stay or indications for cesarean delivery. Maternal total hospital length of stay was longer in the intervention group, whereas inductions for hypertensive disorders were greater in the expectant management group, the authors report.
“The consistent message from the expanding literature on this topic is that there are and will continue to be important tradeoffs 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 authors write.
“Most clinicians believe that induction of labor increases cesareans, and while not statistically significant, that is what this study found,” according to Aaron B. Caughey, MD, PhD, professor and chair of the Department of Obstetrics and Gynecology and associate dean for Women’s Health Research and Policy at Oregon Health & Science University, Portland, who was not involved in the research.
“Interestingly, there are other data that do not support an increase in cesareans with induction of labor; however, it is likely the surrounding practice would drive the cesarean rate,” Dr Caughey said. “In this study, the authors kept to protocols related to cesarean for failure to progress in labor which are not consistent with current recommendations. For example, with no cervical change for 2 hours at 4 cm dilated, where current recommendations are at least 4 hours of no cervical change at least 6 cm or more,” he explained. “Because one can get to 4 cm with induction and not be in active labor, this could have contributed to the increased rate of cesareans in this study.”
On its own, this study is not large enough to drive practice, Dr Caughey said, noting, however, that the findings “underscore the idea that elective induction of labor should not be routinely used until we demonstrate that it is beneficial or at least of no harm.”