Randomised, triple-blind, placebo-controlled trial of atosiban in women with previous embryo implantation failure and abnormal uterine contractions undergoing single blastocyst-stage embryo transfer: a study protocol.

introductionAtosiban may confer therapeutic benefits to specific subpopulations in assisted reproductive technology. The Phase I Atosiban study indicated potential improvements in live birth rates among women with previous implantation failure undergoing frozen-thawed blastocyst transfer who exhibited abnormal uterine contractions, although these findings did not reach statistical significance. Therefore, further investigations are warranted to thoroughly elucidate the efficacy of atosiban and to evaluate whether uterine contractions can serve as a reliable biomarker for its targeted application. METHODS AND ANALYSIS: This is a single-centre, randomised, triple-blind, placebo-controlled trial aiming to enrol 792 infertile women aged 20-40 years with a history of at least one previous embryo implantation failure and abnormal uterine contractions prior to single blastocyst-stage embryo transfer. Eligible participants will be randomly assigned in a 1:1 ratio to receive either intravenous atosiban or a placebo before embryo transfer. The primary outcome is live birth rate, with secondary outcomes encompassing various pregnancy and perinatal parameters. Randomisation will be stratified by age and transfer type. Intention-to-treat analysis will be performed using generalised linear models. The trial will be monitored by an independent data and safety monitoring committee, including one interim analysis. ETHICS AND DISSEMINATION: This study has been approved by the Institutional Ethics Committee of Northwest Women's and Children's Hospital (No. 2025-058-02). Written informed consent will be obtained from all participants. The study results will be disseminated at scientific conferences and published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT07185230.