Influence of vitrification method on clinical outcome of human frozen-thawed cleaved embryo transfer

Objective To investigate the influence of vitrification method on clinical outcome of human frozen-thawed cleaved embryo transfer.Methods In the in vitro fertilization and embryo transfer cycles,supernumerary embryos were cryopreserved by vitrification or slow-freezing sequencing method.The embryo survival rate,intact survival rate,pregnant rate and implantation rate were compared after thawing.Results In 248 vitrified embryo thaw cycles,746 vitrified embryos were thawed,and 643(86.2％) of them survived and 594(79.4％) of them intactly survived after the thawing.In 244 women,632 embryos were transferred,and 107(43.9％) of them got clinical pregnancy,the implantation rate was 26.1％ (165/632).As to slow-freezing method,in 225 embryo thaw cycles,818 embryos were thawed,598 (73.1％) of them survived,436(53.3％) of them intactly survived,and 594 embryos were transferred in 225 cycles,and 74 (32.9％) of them got clinical pregnancy,the implantation rate was 15.2％(90/594).The embryo survival rate,intact survival rate,pregnant rate,implantation rate were higher in vitrification group than those in slow-freezing group (P ＜ 0.05).Conclusion Vitrification is a more effective method of cryopreserving the human embryo than conventional slow freezing. Key words: Vitrification;  Slow-freezing sequencing;  Cleaved embryo;  In vitro fertilization and embryo transfer