A randomized trial of synthetic osmotic cervical dilator for induction of labor vs dinoprostone vaginal insert

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BACKGROUND: Induction of labor is a commonly performed obstetrical intervention. Vaginal prostaglandin E2 (dinoprostone) is a first-choice agent. Mechanical methods of induction are slower in achieving cervical ripening but have a lower risk of adverse effects. OBJECTIVE: This study aimed to compare the efficacy, maternal and neonatal safety, and maternal satisfaction of a synthetic osmotic cervical dilator (Dilapan-S) with those of dinoprostone. STUDY DESIGN: This was an open-label superiority randomized controlled trial in 4 English hospitals. Eligible participants were women ≥16 years of age undergoing induction of labor for a singleton pregnancy at ≥37 weeks’ gestation with vertex presentation and intact membranes. The women were randomly assigned to receive either Dilapan-S or dinoprostone using a telephone randomization system minimized by hospital, parity, body mass index, and maternal age. The induction agent was replaced as required until the cervix was assessed as favorable for labor by the Bishop score. The primary outcome was failure to achieve vaginal delivery (ieor a cesarean delivery being performed). The secondary outcome measures included maternal and neonatal adverse events. Analysis was by intention-to-treat, adjusting for design variables where possible. RESULTS: Between December 19, 2017 and January 26, 2021, 674 women were randomized (337 to Dilapan-S, and 337 to dinoprostone). The trial did not reach its planned sample size of 860 participants because of restrictions on research during the COVID-19 pandemic. The primary outcome was missing for 2 women in the dinoprostone group. Failure to achieve vaginal delivery (or a cesarean delivery being performed) occurred in 126 women (37.4%) allocated to Dilapan-S and in 115 (34.3%) women allocated to dinoprostone (adjusted risk difference, 0.02; 95% confidence interval, −0.05 to 0.10). There were similar maternal and neonatal adverse events between the groups. CONCLUSION: Women undergoing induction of labor with Dilapan-S have similar rates of cesarean delivery and maternal and neonatal adverse events compared with dinoprostone.

Original languageEnglish
Article number100628
Number of pages20
JournalAmerican Journal of Obstetrics & Gynecology Maternal Fetal Medicine
Issue number4
Early online date28 Mar 2022
Publication statusE-pub ahead of print - 28 Mar 2022


  • Pregnancy
  • cervical ripening
  • labor, induced
  • dinoprostone
  • Cesarean section
  • randomized controlled trial


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