The effect of blastomere damage rate on the clinical outcome in frozen-thawed embryo transfer cycles

Objective: To investigate the effects of the blastomere damage on the clinical outcome in frozen-thawed embryo transfer(FET) cycles.Methods: A retrospective analysis was performed in our center on 181 frozen-thawed embryo transfer cycles.The relationship between embryo quality and the damage rate of blastomere cells was analyzed.Pregnancy rate and implantation rate of transferred embryos at different grades of damage(fully intact embryo,embryo with ≤20% and 20% blastomere cells damaged) were evaluated,and the pregnancy and implantation rates of transferred embryos with six or more cells and less than six cells were compared.Results: Embryo survival rate and blastomere cell damage rate were significantly different between grade1,2 and 3 embryo groups,respectively (P0.05 for the survival rate and P0.001 for the damage rate).Higher clinical pregnancy and implantation rates were observed when all transferred embryos were classified as fully intact blastomere,as compared to those of embryos with ≤20% and 20% blastomere cells damaged(P0.05 and P0.01,respectively).The clinical pregnancy and implantation rates of transferred embryos with six or more cells were significantly higher than those of embryos with less than six cells(P0.05).Conclusions: The damage rate of blastomere cells is better for the evaluation of the extent of embryo damage than embryo survival rate.Embryo quality,development stage of transferred embryo and the extent of blastomere damage are the most important embryological factors influencing the pregnancy rate and implantation rate in FET cycles.