SUMMARY. The efficiency of in vitro fertilization and embryos transfer in humans is low: less than 50 % of transplanted embryos reach their potential development. Therefore, there is a problem of early determination of the embryo potential, which precedes the selection of high morphological and chromosomal qualities at the stage of a blastocyst. In 16–18 hours after ICSI micromanipulation, the fertility quality was evaluated for the presence of pronuclei using Z-evaluation. We examined the size and placement of pronuclei relative to the cell center, the number of nucleoli and their distribution. The best development and therefore the greatest potential for implantation were detected in embryos that developed from zygote Z1. Zygotes Z2 and Z3 also formed blastocysts of AA quality on the fifth day. None of the fertilized egg cells that formed zygote Z4 developed into an embryo. We found out that the highest number of embryos with a normal quantity of studied chromosomes was formed from zygotes of Z1 and Z2 categories, and a significant difference was found between the numbers of embryos, in which aneuploidy has not been identified, formed from zygotes of Z1, Z2, Z3 categories, compared to zygotes of type Z4.
Keywords: zygote, quality of embryos, blastocyst, assistant reproductive technologies
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