Clarification of Critical Parameters for the Successful Outcome of Stimulated Cycles of Infertility Treatment

Objective: To improve methods for overcoming infertility, the question of the influence of women’s age on the quality of oocytes and the probability of obtaining euploid blastocysts remains important. The vulnerability of oogenesis in humans is determined by a long period of rest, known as the dictyotene, at the diplotene stage of the meiotic prophase. Although 35 years is traditionally considered the critical age for the increase in the proportion of embryos with numerical chromosomal abnormalities, recent data, including our preliminary results, indicate the need to clarify the age threshold. The aim of this study was to determine the number of oocytes required to produce one euploid blastocyst, as well as to test the hypothesis about the need to identify an older age group with an increasing risk of developing numerical chromosomal pathologies in embryos for women aged 37 years and older. Methods: 798 cycles were analyzed: 6180 mature oocytes (MII), from which 2910 blastocysts developed, 842 of which, according to the results of molecular genetic analysis using the NGS method, had a balanced set of chromosomes. All embryos were divided into 4 groups depending on the woman’s age and the number of MII obtained in the stimulated ART cycle. Results: Data were obtained on the change in the number of mature oocytes, the total number of blastocysts obtained and the number of euploid embryos depending on the age of the woman. We determined the minimum number of ART cycles and the required number of mature oocytes and successfully fertilized zygotes that will allow obtaining at least one euploid blastocyst. Conclusions: The results of the study allowed us to revise the boundaries of the younger age group and include women aged 36 years, as well as to refine predictive tools for assessing the success of infertility treatment for women of different age groups.