Skip to main content
SMFM 2025 Pregnancy Meeting Main banner
Final Program


Program Book
Icon Legend
Presentation Icons
Additional registration fee required
Additional registration fee required
CME Credit Offered
CME Credit Offered
Abstract Award
Abstract Award
Poster Icons
Additional registration fee required
Additional registration fee required
Faculty have requested this content not be shared on social media
Faculty have requested this content not be shared on social media
CME Credit Offered
CME Credit Offered
Abstract Award
Abstract Award
Back

Oral Plenary Session 1

Oral Plenary Session 1

(5) Atosiban versus placebo in threatened preterm birth (APOSTEL 8-study): an international randomized controlled trial

Thursday, January 30, 2025
9:00 AM – 9:15 AM  
Location: Aurora Ballroom, Lobby Level
Abstract Award
Objective: In many countries, threatened preterm birth (PTB) is treated with tocolytics to allow for a complete antenatal course of corticosteroids. Although effective in delaying birth, a positive effect on neonatal outcome has never been demonstrated. We assessed the effectiveness of atosiban for women with threatened PTB between 30 and 34 weeks of gestation in improving neonatal outcome.

Study Design: We performed a randomized double-blind placebo-controlled superiority trial in 26 hospitals in the Netherlands, England and Ireland. After informed consent, women with a singleton or twin pregnancy with threatened PTB between 30 and 34 weeks gestation were randomized (stratified by centre, 1:1 ratio) to intravenous atosiban or placebo for 48 hours. Primary outcome was a neonatal composite of perinatal mortality and morbidity. Treatment effect was expressed as relative risk (RR) with 95% confidence intervals (CI). To detect a reduction from 12% adverse perinatal outcome in the placebo group to 6% in the atosiban group with a power of  80%, we needed to randomise 722 women. Assuming a 5% drop-out rate, the sample size was calculated at 760 participants. Analysis was by intention-to-treat principle.

Results: From December 2017 to July 2023, we randomized 755 participants to atosiban (n=377) or placebo (n=378). Primary outcome was available for 752 participants with 884 infants. The primary outcome occurred in 37/449 (8.2%) infants in the atosiban group and 40/435 (9.2%) in the placebo group (RR 0.90, 95% CI 0.58 to 1.40). There were two (0.4%) and four (0.9%) perinatal deaths respectively (RR 0.48, 95% CI 0.09 to 2.63). There were no significant differences in other neonatal outcomes. Prolongation of pregnancy > 48 hours was significantly more often achieved in the atosiban group (292/375, 77.5%) compared to placebo (261/377, 69.2%) (RR 1.13, 95% CI 1.03 to 1.24).

Conclusion: We did not demonstrate superiority of atosiban over placebo in improving neonatal outcomes as a treatment for threatened PTB between 30 and 34 weeks of gestation. This questions the widespread use of tocolytics in many countries.