SUMMARY. The study was focused on morphokynetic characteristics of in vitro cultured human embryos that were con-sidered to be aneuploid or euploid according to the preimplantation genetic screening results. Among all the embryos examined only 34.2 % were chromosomally balanced, while others possessed isolated or combined chromosome abnormalities. Although morphological features of cleaving pathologic and euploid embryos did not differ significantly, on the fifth day of culture chromosomally balanced specimen formed «expanded» blastocyst twice as frequently as abnormal ones. More-over, development of 38,4 % of aneuploid embryos was compromised before the initiation of cavitation. Thus, prolonged embryo culture advances selection of samples with the highest implantation potential for the transfer on the basis of the morphokynetic characteristics and helps to avoid additional genetic testing.
Keywords: preimplantation genetic screening; chromosome abnormality; human embryo; morphological characteristics