O-100 Incidence, morphology, ploidy and developmental arrest in direct cleavage embryos: what are they teaching us? Morphokinetic analysis of 15.081 embryos

Abstract Study question What is the impact of direct cleavage (DC) occurrence during embryo/blastocyst development regarding morphology grade, embryo arrest and ploidy status? Summary answer Blastocyst formation and morphology grade are significantly reduced in DC when compared to non-DC embryos; however, there is no difference in blastocyst ploidy status. What is known already Chromosome instability leading to aneuploidy during early cleavage is well known in humans. DC is defined as the abrupt cleavage of one into three or more daughter blastomeres as the result from an irregular mitosis. Three or more mitosis poles can impair early embryo development; however, how some embryos with these irregular divisions might be able to develop into expanded blastocysts is still unknown. Time-lapse system provides an uninterrupted evaluation of embryo morphological and dynamic parameters, allowing our understanding in such events and if those embryos may be associated with a self-correction mechanism to reach blastocyst stage. Study design, size, duration Retrospective cohort study from 15.081 embryos, 3.962 cycles and 3.106 patients that were undergoing in vitro fertilization (IVF) treatment according to medical referral in a single private ART center from December 2018 to November 2021. Only two-pronuclear (2PN) embryos cultured in time-lapse incubators (EmbryoScope, Vitrolife, Sweden) were included in the study. Direct cleavage occurance was annotated when a single blastomere directly cleaved into three or more daughter blastomeres. Participants/materials, setting, methods DC embryos were also classified in DC 1-3: abnormal cleavage occurred in zygote (1-cell) resulting in 3–4 blastomeres and in DC 2+: abnormal cleavage occurred at the 2-cell stage resulting in 5 or 6 blastomeres. Embryo arrest, blastocyst formation rate and morphology grade (Gardner and Schoolcraft, 1999) were annotated. Blastocyst biopsy reports for ploidy status were also considered for analysis. Mann-Whitney, chi-squared and Fisher tests were applied for statistical analysis. p