Embryological Characteristics and Preimplantation Genetic Testing for Aneuploidy of Embryos Derived from Cryopreserved Oocytes of Women of Different Reproductive Ages

Oocyte vitrification is widely used for female fertility preservation. However, the efficacy of this procedure may depend on the women's age. The aim of the study was to compare the morphology, viability of cryopreserved oocytes, and their fertilization outcomes (fertilization, blastulation rate, level of embryo chromosomal aneuploidy-preimplantation genetic testing for aneuploidy [PGT-A]) in women of different reproductive ages. The studied oocytes were divided into groups depending on the age of patients: up to 30 years (group 1), 30-35 years (group 2), 36-40 years (group 3), and older than 40 years (group 4). It has been shown that in women of older reproductive age, the number of oocytes with polymorphism of endo- and extracytoplasmic structures was higher compared with younger patients. This could reflect on their cryosurvival rate, which was the highest in group 1 (98.1%) and the lowest was in group 4 (47.4%). With increasing age, the fertilization rate of cryopreserved oocytes and subsequent blastulation was decreased. However, the number of embryos with an aneuploid chromosome set number was increased. The chromosome set number euploidy rate of the embryos obtained from cryopreserved oocytes of advanced age women (group 4) did not differ from the fresh group with the same age (31.2% vs. 24.4%, p > 0.05), but the number of euploid embryos per patient was less than one (0.8 +/- 0.1). Therefore, the decision to cryopreserve the oocytes of a patient of older reproductive age should be made individually for each situation, taking into account the prospects of obtaining full-fledged embryos and the chances of pregnancy.