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

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Background: Induction of labor is a commonly performed obstetric intervention. Vaginal prostaglandin E2 (dinoprostone) is a first-choice agent. Mechanical methods of induction are slower to achieve cervical ripening but have a lower risk of adverse effects.

Objective: To compare the efficacy, maternal and neonatal safety, and maternal satisfaction of a synthetic osmotic cervical dilator (Dilapan-S) with dinoprostone.

Study Design: This was an open-label, superiority randomized controlled trial in four English hospitals. Eligible participants were women ≥ 16 years of age undergoing induction of labor for a singleton pregnancy, ≥ 37 weeks’ gestation with vertex presentation and intact membranes. Women were randomly assigned to receive Dilapan-S or dinoprostone using a telephone randomization system minimized by hospital, parity, BMI and maternal age. The induction agent was replaced as required until the cervix was assessed as favorable for labor by Bishop score. The primary outcome was failure to achieve vaginal delivery (i.e. Cesarean delivery). Secondary outcome measures included maternal and neonatal adverse events. Analysis was by intention-to-treat, adjusting for design variables where possible.

Results: Between 19 December 2017 and 26 January 2021, 674 women were randomized (337 to Dilapan-S and 337 to dinoprostone). The trial did not reach its planned sample size of 860 due to restrictions on research during the Covid-19 pandemic.

The primary outcome was missing for two women in the dinoprostone group. Failure to achieve vaginal delivery (Cesarean section) occurred in 126 women (37.4%) allocated to Dilapan-S, and 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 caesarean section and maternal and neonatal adverse events compared to dinoprostone.
Original languageEnglish
Article number100628
JournalAmerican Journal of Obstetrics & Gynecology Maternal Fetal Medicine
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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