Misoprostol with balloon vs oxytocin with balloon in high-risk pregnancy induction: a randomized controlled trial

Pregnancies at high risk for maternal, fetal, or placental complications often necessitate induction of labor in the late preterm or early term period for delivery. Limited data exist on the safest method of induction to use in this specific patient population.

This study aimed to compare the combination of oxytocin plus a Cook balloon vs misoprostol plus a Cook balloon for induction of labor in high-risk pregnancies.

We conducted an open-label, randomized controlled trial at a single institution from July 2020 to May 2022. The study was approved by the institutional review board and registered with ClinicalTrials.gov (NCT04492072). Individuals with a high-risk pregnancy, at least ≥22 weeks' gestation, with a singleton in cephalic presentation, Bishop score ≤6, and intact membranes were offered enrollment. A high-risk pregnancy was defined as a pregnancy with any of the following complications: hypertensive disease of pregnancy, fetal growth restriction, oligohydramnios, suspected placental abruption requiring delivery, uncontrolled pregestational diabetes, or abnormal biophysical profile or nonstress test requiring delivery. The primary outcome was the rate of cesarean delivery. Secondary maternal outcomes included induction to delivery interval, number of vaginal deliveries within 24 hours, rates of uterine tachysystole, intraamniotic infection, operative vaginal delivery, and postpartum hemorrhage. Secondary fetal outcomes included fetal heart rate abnormalities, stillbirth, Apgar scores <7 at 5 minutes, admission to the neonatal intensive care unit, arterial umbilical blood pH <7.1, sepsis, and neonatal death. A subgroup analysis was planned for the primary outcome to assess the different indications for cesarean delivery. An intent-to-treat analysis was performed.

During the 22 months of the trial, a total of 150 patients were randomized, and 73 (49%) of those were induced with oxytocin and a Cook balloon and 77 (51%) were induced with misoprostol and a Cook balloon. There was no significant difference in the overall rate of cesarean delivery between the study groups, (21.9% vs 31.1%; relative risk, 0.70; 95% confidence interval, 0.41-1.21), nor among those for which the cesarean delivery was performed for a specific indication. There were no differences in the secondary maternal and fetal or neonatal adverse outcomes.

In high-risk pregnancies, the rate of cesarean delivery and adverse maternal and fetal outcomes were similar for induction of labor with oxytocin and a Cook balloon and for induction with misoprostol and a Cook balloon.