P-232 The developmental potential of human embryos with subtypes of multinucleation in cleavage stages

Abstract Study question Does subtypes of multinucleation in cleavage stage affect the developmental and implantation potential of human embryos? Summary answer Different subtypes of multinucleation presented diverse effects on morphokinetic abnormality and blastocyst rate, but achieved comparable implantation rate with blastocysts transfer. What is known already Time-lapse images reveals many abnormal events in early embryonic development. Blastomere multinucleation (MN) has the highest incidence, thus attracts extensive attention. More and more studies have been conducted on the generation mechanism, reproductive potential and utilization value of multinucleation embryos, but the impact of different subtypes of MN on embryo developmental potential, morphokinetics and clinical outcomes have not been well identified. Study design, size, duration Using a time-lapse incubator (EmbryoScope plus), we retrospectively explored the associations between the subtypes of MN with morphokinetic parameters, blastocyst rate and clinical pregnancy. This study assessed 4416 embryos, including 628 MN embryos from single embryo transfers after 1521 ICSI cycles conducted in Reproductive Medical Center of the First Affiliated Hospital of Hainan Medical University between October 2019 and October 2021. Participants/materials, setting, methods ubtypes of MN, morphokinetic parameters, blastocyst rate, preimplantation genetic testing for aneuploidy (PGT-A) result and clinical pregnancy were studied retrospectively. The quantitative variables were expressed as mean SD and were compared by means of Student two-sample t test. The categoric variables were expressed as frequency and percentage and were compared between groups by means of Pearson chi-square test or Fisher exact test. Main results and the role of chance The rate of MN was the highest (14.22%) among abnormal events. The blastocyst rate of MN embryos was significantly reduced (52.48%). The blastocyst rate of MN at 2-cell stage was significantly higher than that at 4-cell stage, but there was no significant difference in euploid rate and implantation rate with single blastocyst transfer. We chose embryos with only one blastomere multinucleation (MN-1) at 2-cell stage to analyze the effect of subtypes of MN, including two equal size nuclei (Bi-), two unequal size nuclei (micro-), more than two equal nuclei (poly-) and more than two unequal nuclei (cluster-), on developmental and implantation potential of human embryos. There were significant morphokinetic delay and reduced blastocyst rate in cluster-nucleation and poly-nucleation groups, but they could achieve competence implantation rate after blastocyst transfer. It was interesting that when we separately analyze the MN embryos which could survive to blastocyst, the morphokinetic data didn’t show significant delay in micro-nucleation group, only the cleavage time to the 3-cell stage was significant longer in Bi-nucleation group, and the time of pronuclear fading and cleavage time to the 2-cell stage were significant longer in poly-nucleation group. Limitations, reasons for caution The population size was relatively small and the current study is restricted by its retrospective nature and absence of live birth information. Wider implications of the findings It would be interesting to explore, prospectively in multi-clinics, whether these subtypes of multinucleation embryos equal to non-multinucleation embryos with blastocyst transfer. Further studies are needed, notably to explore the underline "self-repair" mechanism of Blastomere multinucleation. Trial registration number 0