Time from insertion to expulsion of cervical ripening balloon in preterm versus term inductions of labor

Preterm induction of labor can be necessary for maternal and fetal wellbeing. Duration of cervical ripening balloon (CRB) use has been studied in only term inductions. Our study investigated duration of time in hours for CRB expulsion and vaginal delivery in preterm inductions of labor.

This was a single-institution retrospective cohort study of preterm (< 37 weeks) and term (≥ 37 weeks) inductions with CRB between 2010 and 2021. Cesarean deliveries were excluded. Primary outcome was insertion to expulsion time of CRB. Secondary outcomes included induction to delivery time, cervical dilation after expulsion, misoprostol, and Pitocin use. Institutional review board (IRB) approval was obtained prior to the study.

Ninety-eight patients with vaginal delivery after preterm CRB use were identified and matched 1:1 on baseline characteristics (p > 0.05) to term patients with vaginal delivery after CRB use. Mean insertion to expulsion time was significantly shorter for term than preterm inductions (mean 7.2 ± 3.09 h versus 8.5 ± 3.38 h; p < 0.01). Mean induction to delivery time was significantly shorter for term than preterm inductions (18.4 ± 7.6 h versus 22.5 ± 9.01 h; p < 0.01). Increased use of misoprostol, Pitocin, and second CRB were noted among the preterm cohort. Among term patients, more CRB placement at start of induction and greater cervical dilation post-balloon were found in comparison to preterm patients.

Among patients undergoing preterm induction, longer insertion to expulsion time of CRB, longer induction to delivery time, and increased interventions should be expected. Different standards for labor management should be considered for achieving vaginal delivery in preterm inductions.