Double Vitrification-Warming Cycles Reduce Live Birth Rates in Single Euploid Blastocyst Transfers: A Retrospective Cohort Study

Objectives: To evaluate the impact of blastocysts biopsied once and vitrified twice on clinical outcomes. Methods: This retrospective study analyzed 277 single euploid blastocyst transfer cycles conducted at the Center for Assisted Reproduction, 16A Ha Dong General Hospital, from March 2018 to January 2024. Cycles were stratified into two groups: Group BV (biopsied once, vitrified once; n = 207) and Group VBV (biopsied once, vitrified twice; n = 70). Pregnancy outcomes were compared between groups, and a binary logistic regression model identified variables associated with live birth rates. Results: Group BV demonstrated superior outcomes compared to Group VBV across all metrics: implantation rate (55.6% vs. 37.1%, p < 0.001), clinical pregnancy rate (55.1% vs. 37.1%, p < 0.001), ongoing pregnancy rate (54.1% vs. 35.7%, p < 0.001), and live birth rate (53.6% vs. 35.7%, p = 0.01). The number of vitrification-warming cycles was the only factor significantly associated with reduced live birth rates (OR 1.95, 95% CI 1.01–3.78, p < 0.05). Conclusions: An additional vitrification-warming cycle significantly reduces pregnancy success in single euploid blastocyst transfers. Patients undergoing PGT-A should be explicitly counseled about the potential decline in success rates if previously vitrified blastocysts undergo repeated warming cycles for diagnostic confirmation.