Balloon catheters versus vaginal prostaglandins for induction of labor (CPI Collaborative): a meta-analysis of individual participant data from randomized controlled trials


Induction of labor is one of the most common obstetric interventions in the world. Balloon catheters and vaginal prostaglandins are widely used to ripen the cervix during labor induction. We sought to compare the efficacy and safety profiles of these two induction methods.


We performed a meta-analysis of individual participant data comparing balloon catheters and vaginal prostaglandins for cervical ripening before labor induction. We systematically identified published and unpublished randomized controlled trials that completed data collection between 19 March 2019 and 1 May 2021, by searching the Cochrane Library,, the International Registry Platform for WHO clinical trials and PubMed. Other trials conducted before March 19, 2019 were identified through a recent Cochrane review. Data for the combined use of the two methods were not included, only data from women with a single viable pregnancy were analyzed, and no exclusions were made on the basis of parity or state of the membrane. We contacted individual trial authors and participant-level data were harmonized and recoded according to predefined variable definitions. Risk of bias was assessed with the ROB2 tool. The primary outcomes were cesarean delivery, indication for cesarean delivery, composite adverse perinatal outcome, and composite adverse maternal outcome. We followed the intention-to-treat principle for the primary analysis. The primary meta-analysis used two-step random-effects models and the sensitivity analysis used one-step mixed models. All models were adjusted for maternal age and parity. This meta-analysis is registered with PROSPERO (CRD42020179924).


Individual participant data were available from 12 studies with a total of 5460 participants. Balloon catheters, compared to vaginal prostaglandins, did not lead to a significantly different rate of cesarean delivery (12 trials, 5414 women; crude incidence 27.0%; adjusted OR [aOR] 1 09, 95% CI 0 95–1 24; I2=0%), cesarean delivery for delayed progression (11 trials, 4601 women; aOR 1 20, 95% CI 0 91–1 58; I2=39%), or cesarean delivery for fetal distress (10 trials, 4441 women; aOR 0.86, 95% CI 0.71–1.04; I2=0%). Composite adverse perinatal outcome was lower in women assigned to balloon catheters than in those assigned to vaginal prostaglandins (ten trials, 4452 neonates, crude incidence 13.6%; aOR 0 80, 95% CI 0 70–0 92; I2=0%). There was no significant difference in composite adverse maternal outcome (ten trials, 4326 women, crude incidence 22.7%; aOR 1.02, 95% CI 0.89–1.18; I2=0%).


In induction of labor, balloon catheters and vaginal prostaglandins have comparable cesarean delivery rates and maternal safety profiles, but balloon catheters result in fewer adverse perinatal events.


Australian National Health and Medical Research Council and Monash Health Emerging Researcher Fellowship.