Induction success or failure: Does maternal age matter?

Results of a new retrospective study show that among nulliparous women, older maternal age does not increase the risks for failing labor induction with a prostaglandin E2 vaginal insert or for cesarean delivery.¹

Conducted by researchers at the Rabin Medical Center, Petach-Tikva, Israel, the study included data from 537 nulliparous women with a Bishop score ≤7 at 34+0 to 41+6 gestational weeks who underwent labor induction using a 10 mg dinoprostone vaginal insert. Of the total population, 69 (12.8%) were “older,” defined as aged ≥35 years.

Overall, the labor induction failure rate was 27.6%, and in a univariate analysis, it was not significantly different comparing the older women and the control group comprised of the 468 women aged <35 years (26.5% vs 34.8%; P=.502). The rate of cesarean delivery was significantly higher among the older women than in the controls (36.2% vs 21.4%; P=.009). However, in a regression analysis adjusting for potential confounders that included maternal body mass index, indication for delivery, birth weight, and gestational age at delivery, older age was not associated with an increased risk of either outcome. Short term neonatal morbidity was also not significantly different between the two study groups.

“Based on our study, we believe that physicians should not be afraid to offer labor induction to women simply because they are of advanced maternal age. In considering the need for a priori cesarean section in these older nulliparous women, the decision should be individually tailored by taking into account other obstetrical and personal characteristics,” said Liran Hiersch, MD.

Also see: Outpatient cerivcal ripening: Has its time come?

Dr Hiersch is a physician in the Department of Obstetrics and Gynecology, Rabin Medical Center, and a researcher, Sackler School of Medicine, Tel Aviv University, Israel. He conducted the study in collaboration with Eran Hadar, MD, and Rinat Gabbay-Benziv, MD.

Women were excluded from the study if the pregnancy was complicated by non-vertex presentation, multiple gestations, or chromosomal or major structural anomalies.  A majority of women (53.4%) in the study population underwent induction of labor for fetal indications (eg., suspected fetal growth restriction below the 10^th percentile, oligohydramnios, fetal macrosomia, cholestasis of pregnancy, or pregnancy beyond 41 gestational weeks.

Dr Hiersch noted that while prior studies investigated outcomes of labor induction among women who were of advanced maternal age or who were nulliparous, there was a place for a study to address whether the combination of both obstetrical risk factors affected the labor induction failure rate.

“The fact that over the last several decades, women have increasingly decided to postpone their first pregnancy makes our cohort more relevant than before,” Dr Hiersch told Contemporary OB/GYN.

As another difference compared with other studies that have investigated outcomes of labor induction, the current study also included a cohort of women who received the prostaglandin E2 insert.

“Other studies did not distinguish among the different methods available for labor induction. We think clinicians can benefit from the findings of our study that specifically addressed use of the prostaglandin E2 vaginal insert,” Dr Hiersch said.

He acknowledged that the research has limitations because of its retrospective design. Consequently, information was missing on some factors that may contribute to labor induction failure, such as maternal gestational weight gain. In addition, the group of older nulliparous women was relatively small.

“As an important strength, however, our study was conducted in a single center where a uniform protocol for labor induction is in place,” Dr Hiersch said.

According to the center’s protocol for labor induction, a 10 mg dinoprostone slow-release vaginal insert is placed to the vaginal posterior fornix and continued for up to 24 hours. It is removed earlier if the Bishop score is >7 or if there is uterine tachysystole or a non-reassuring fetal heart rate on monitoring. Among the 148 women who failed labor induction, an unfavorable Bishop score at 24 hours after prostaglandin E2 vaginal insert placement was the most common reason (74.3%).

The 537 women included in the study represented 3.5% of a total of 15,564 deliveries at the medical center during the 3-year study period from January 2012 to December 2014.

Reference

1. Hadar E, Hiersch L, Ashwal E, et al. Induction of labor in elderly nulliparous women. J Matern Fetal Neonatal Med. 2016 Sep 27:1-17. [Epub ahead of print]