Age-Related Increase in Live-Birth Rates of First Frozen Thaw Embryo Compared With First Fresh Transfer in Initial Assisted Reproductive Technology Cycles Without Preimplantation Genetic Testing [ID 2683417

Abstract

INTRODUCTION: Compare live-birth outcomes stratified by age between primary frozen (FET) and fresh transfers in initial autologous assisted reproductive technology (ART) cycles without preimplantation genetic testing (PGT). METHODS: This was a retrospective cohort study of autologous first ART cycles without PGT comparing success rates of primary embryo transfer (frozen thaw versus fresh) from the 2014–2020 SARTCORS database. We compared live-birth rate (LBR) stratified by age and cumulative live-birth rate (CLBR) for first FET versus first fresh cycles in first ART cycle. Primary transfer (FET or fresh) was the first transfer for an index retrieval. LBR was number of live births from first embryo transfer associated with first retrieval. CLBR was defined as at least one live birth from all linked embryo transfers within 1 year from initial retrieval. Multivariate logistic regression (MLR) determined association between live-birth outcomes and method of transfer. RESULTS: 228,171 first ART cycles resulted in primary embryo transfer. 62,100 initial FETs and 166,071 fresh transfers were compared. LBR was 48.3% for initial FETs versus 39.8% for initial fresh transfers (P<.001). CLBR was 71.8% for initial FETs versus 59.2% for initial fresh transfers (P<.001). MLR demonstrated that initial FETs had a greater chance of live birth across all age groups, with adjusted odds ratio of live birth incrementally increasing with advancing age groups. CONCLUSION: Overall, LBR and CLBR were greater for first FET than fresh transfers with incremental increases in odds of live birth with advancing age, suggesting the presence of a more favorable age-related change in endometrial receptivity present in frozen–thawed cycles.