Clinical Outcome Of Day 3 Cleavage Slow-growing Embryos At Different Cleavage Rates After Overnight Culture

Background To explore the association between clinical outcomes and cleavage rate of day 3cleavage slow-growing embryos after overnight culture.Methods A retrospective cohort study was conducted between January 2017 and July 2019.The data collected from 303 frozen embryo transfer cycles with 606 either 4-cell or 5-cell embryos cultured overnight(18-22h)after thawing were analyzed.Based on the growth rate after overnight culture,embryos were divided into 3 groups: no embryo reaching 8 cells(group A),either one of the two embryos reaching 8 cells(group B)and both two embryos at least reaching 8 cells(group C).Statistical analysis of different clinical outcomes among three groups was performed.Results β-HCG positive rate(OR 3.22;p=0.001),implantation rate(OR 2.44;p=0.002),clinical pregnancy rate(OR 3.04;p=0.001),ongoing pregnancy rate(OR 3.14;p=0.001)and live birth rate(OR 2.78;p=0.004)were significantly higher in Group C compared to Group A.Group B has a significantly higher biochemical pregnancy rate(OR 2.02;p=0.013)and implantation rate(OR 1.77;p=0.019)than Group I.There was no notable difference in multiple pregnancy rate and miscarriage rate among the three groups(p>0.05).Conclusions After overnight culture of the slow-growing cleavage embryos on day 3,the group with two 8-cell embryos obtained a better pregnancy outcome than no 8-cell group or one 8-cell group.