Cumulative live births and predictive factors of emergency oocyte cryopreservation: a retrospective cohort study.

Background: Oocyte vitrification, a widely utilized assisted reproductive technology for fertility preservation, can address emergencies arising from the unavailability of sperm from the male partner on the day of oocyte retrieval. However, the infrequent and unpredictable nature of emergency oocyte cryopreservation leads to a scarcity of literature on its reproductive outcomes, complicating the provision of informed patient counseling.

Methods: This study, conducted between January 2017 and December 2022, included 137 emergency oocyte cryopreservation cycles involving 136 patients and their respective thawed cycles. Descriptive statistics were used to analyze cycle characteristics and oocyte thaw and transfer outcomes, grouped by indication of oocyte vitrification. Univariate and multivariate analyses were performed to identify predictors associated with reproductive outcomes by indication of oocyte vitrification.

Results: A total of 137 emergency oocyte cryopreservation-thaw cycles were analyzed, with a median oocyte survival rate of 84.2%, fertilization rate of 57.7%, and high-quality Day-3 embryo formation rate of 33.3%. Of all cycles, 15.3% resulted in no transferable embryos. The cumulative live birth rate (CLBR) for the entire cohort was 29.2%, with 40 live births achieved through both fresh and frozen embryo transfers. Stratified analysis revealed that cycles due to absolute male factor infertility had higher reproductive efficiency, including more oocytes retrieved, a greater number of high-quality embryos, higher implantation rates, and a CLBR of 39.5%, compared to 11.8% in the relative male factor group. Multivariate analysis identified female age, infertility duration, sperm source, number of mature oocytes retrieved and the presence of male infertility factors as key determinants of live birth outcomes.

Conclusions: Emergency oocyte vitrification yielded a cumulative live birth rate of 29.2%, with rates differing by clinical indication: 39.5% in the absolute male factor group and 11.8% in the relative male factor group. Moreover, the factors associated with reduced live birth rates differed depending on the underlying indication for vitrification. These findings support the clinical utility of emergency oocyte vitrification and underscore the significant contributions of both female and male factors to reproductive outcomes of oocyte cryopreservation.