ABSTRACT
Objective To investigate the effect of laser artificial shrinkage(LAS)on pregnancy outcome in vitrification of human expanded blastocysts.Methods We selected 3859 frozen-thawed blastocyst-stage embryo transfers from January 2014 to December 2015.The transfers were divided into LAS group(n=3 176)and non-LAS group(n=683),which were then subdivided into ＜36 y subgroup and ≥36 y subgroup according to their age.Main outcomes measures were thawing rate,implantation rate and clinical pregnancy rate.Results Thawing rate, clinical pregnancy rate and implantation rate were 97.32%(5 453/5 603),66.81%(2 118/3 170),and 53.55%(2 912/5 438)in LAS group.In non-shrink group,they were 95.13%(1 173/1 233),62.70%(427/681),and 49.74%(582/1 170),which did not significantly differ from those in the former group(P＜0.05).Further analysis of the subgroups showed that thawing rate was significantly higher in LAS group than in non-shrink group of patients＜36 y(97.27% vs.95.33%;P＜0.05).Thawing rate and biochemical pregnancy rate were significantly higher in LAS group than in non-shrink group in patients ≥36 y(97.75% vs.93.66%;65.45% vs.50.65%,P＜0.05). Cancellation rate was not significantly different between the two groups(0.19% vs.0.29%, P ＞ 0.05). Conclusion LAS technique can increase thawing rate,clinical pregnancy rate and implantation rate before cryopreservation of blastocysts.