Analysis of clinical outcome of 941 frozen-thawed embryo transfer cycles with different cryopreservation duration of vitrified embryos

Objective:To evaluate the influence of cryopreservation duration on quality of frozen-thawed Day 3embryo and pregnancy outcome in frozen-thawed embryo transfer(FET)cycles.Methods:In this retrospective study,941 FET cycles were divided into 3groups according to the storage duration of vitrified embryos:(1-9)months(749cycles),(9-16)months(144cycles),≥16month(48cycles).The rates of embryos survival,fully intact blastomere,substantially intact blastomere,biochemical pregnancy,clinical pregnancy and implantation were evaluated.Results:Among the three groups,the survival rates were 98.22%,98.06% and 96.33%;fully intact blastomere rates 86.95%,82.58%and 88.07%;substantially intact blastomere rates 10.78%,14.19%and7.33%;biochemical pregnancy rate 62.22%,54.17% and 54.17%;clinical pregnant rates 58.74%,49.31% and 52.08%;implantation rates 40.53%,33.22% and 37.23%,respectively.There were no significant differences in all observed parameters among the three groups(P0.05).Conclusions:Within the studied cryopreservation duration of vitrified embryo,the storage duration does not affect the quality of frozen-thawed embryo and the pregnancy outcomes of FET cycles.