Clinical Research Directory

Fresh Versus Vitrified-Warmed Donor Oocytes: Embryological and Clinical Outcomes

This multicenter retrospective observational study compares embryological and clinical outcomes following treatment with fresh versus vitrified-warmed donor oocytes at Bocian Fertility Clinic centers in Poland. The study focuses on a standardized allocation strategy in which recipients are intended to receive six mature (metaphase II, MII) donor oocytes. In the vitrified-warmed group, oocytes are cryopreserved at the MII stage and subsequently warmed for use. Oocytes lost during warming are not routinely replaced, allowing the study to evaluate the consequences of warming-related losses within the initial allocation. The study will assess fertilization, embryo development, usable blastocyst yield, the probability of obtaining an embryo for transfer, and live birth following the first embryo transfer originating from the allocated oocytes. Clinical effectiveness will be evaluated from the initial oocyte allocation, including cycles in which no embryo transfer occurs. The objective is to determine whether fresh and vitrified-warmed donor-oocyte strategies are associated with differences in embryological efficiency and the likelihood of live birth when the initial number of mature allocated oocytes is standardized.