Oral prostaglandin safer than vaginal for induction?

Labor induction using an oral prostaglandin solution is less effective than a vaginal prostaglandin gel for achieving vaginal birth within 24 hours, but is a safer option because it is associated with a lower rate of cesarean delivery, according to the results of a new retrospective study.¹

“CS [cesarean delivery] increases risks for maternal complications of placenta previa, placenta accreta, massive obstetric bleeding, and peripartal hysterectomy, and the risk of CS is increased by labor induction and after a woman delivers by CS,” said Ylva Vladic Stjernholm, Docent/Associate Professor, Department of Women’s and Children’s Health, Karolinska University Hospital, Stockholm, Sweden.

“With the goal of minimizing maternal morbidity and mortality, we recommend using an oral prostaglandin rather than a vaginal prostaglandin for labor induction because the oral formulation minimizes the probability for CS.”

The investigators undertook their study recognizing that induced labor rates have been increasing in many areas of the world in the past few decades. In Sweden, the rate more than doubled over a 20-year period from 7% of all childbirths in 1992 to 16% in 2012–2013.

Cases for inclusion in the retrospective study were identified through a search of the obstetric records of women who delivered at the Karolinska University Hospital in 2012 and 2013. The analyses included 252 women who received dinoprostone 2 mg vaginal gel and 265 women who had labor induced with oral misoprostol 25 µg. The vaginal gel prostaglandin was inserted in the posterior vaginal fornix every 6–8 hours for a maximum of 3 doses. The oral prostaglandin first became available in 2013. It was administered in an oral solution of 25 µg/2.5 mL sprayed into the mouth every 2 hours for a maximum of 8 doses.

There were no significant differences between the prostaglandin groups in indications for labor induction, age, gestational age, proportion of women who were primiparous, proportion of women with a previous CS, or overall vaginal birth rates. Statistically significant differences between the oral and vaginal prostaglandin groups were found for outcomes analyses of mean induction to vaginal delivery interval (21.6 vs 18.2 hours, respectively; P<.001), rate of vaginal birth within 24 hours (66% vs 80%, respectively; P <0.001), and CS (32% vs 19%, respectively; P=.002).

Although the oral prostaglandin was associated with a significantly longer induction-to-vaginal delivery interval, it was not associated with increased rates of obstetric bleeding, chorioamnionitis, or neonatal asphyxia compared with the vaginal prostaglandin.

Subgroup analyses were also conducted focusing on primiparous women and those with an unripe cervix as induced labor in women with these features is particularly likely to result in prolonged labor and CS.

“To our knowledge, there are no previous published studies comparing the safety and efficacy of oral and vaginal prostaglandin for labor induction in these subgroups of women,” Dr Stjernholm said.

Statistically significant differences between prostaglandin groups in the rates of vaginal birth within 24 hours and CS persisted in the subgroup analyses. Rates of vaginal birth within 24 hours in the oral and vaginal prostaglandin groups among primiparous women were 54% and 71%, respectively (P=0.01) and were 66% and 79%, respectively (P=0.01) among women with an unripe cervix. CS rates for the oral and vaginal prostaglandin groups among primiparous women were 25% and 41%, respectively (P=0.03) and were 21% and 33%, respectively, (P=0.04) in women with an unripe cervix.

The induction-to-vaginal delivery interval also remained significantly longer using the oral prostaglandin compared with the vaginal formulation among both primiparous women and those with an unripe cervix.

Reference

1. Thorbiörnson A, Vladic T, Stjernholm YV. Oral versus vaginal prostaglandin for labor induction. J Matern Fetal Neonatal Med. 2016;13:1-4. Epub ahead of print.