P-117 The reason why direct cleavage and rapid cleavage should be differentiated

Abstract Study question Direct cleavage (DC) and Rapid (RaC) both appear to be 1 cell divided into 3 (or more) cells, should they distinguished? Summary answer Since blastomeres by RaC had higher developmental potential than DC, since many embryos “normal” blastomere, the two distinguished. What is known already in which one divides three cells without two-cell stage, RaC, or divide rapidly after short stage (The former lead segregation of chromosomes while latter leads inadequate DNA replication), are often recorded as “DC”, but when classified detail, there reports that blastocyst development rate embryos. However, reason for this has not been clarified. design, size, duration This was a retrospective study 643 collected cultured at least 5 days 2020 our clinic. The were time-lapse monitored EmbryoScope (Vitrolife, Sweden) groups according style first division. Participants/materials, setting, methods follows: DC group: have stage; (<5 hours) both) 2-cell Normal (NC) more hours. subsequent all observed whether participated blastocysts recorded. Main results role chance Of embryos, 63 group 199 (173 dividing blastomere 26 two). participation 4.4% group, 19.5% 61.6% normal with significant differences between (p < 0.01). good (4BC Gardner grade) 4.8% (3/63) 40.5% (70/173) (RaC1 group), 19.2% (5/26) such (RaC2 showing difference RaC1 (P live birth single transfer 50% (1/2) 27.8% (5/18) 100% (1/1) RaC2 group. (Note 381 NC above rates 76.5%, 63.3% (241/381), 29.3% (22/75), respectively) Limitations, reasons caution examined only division did consider second divisions. In addition, 2020, clinical use PGT-A approved principle Japan, subject undergone chromosome analysis. Wider implications findings indicated respective presence blastomeres, births obtained so these irregular divisions would completely compromise euploidy. Trial registration number applicable