ABSTRACT
OBJECT: To compare the viability after thawing of cryopreserved embryos according to developmental stage and decide the cryopreservation strategy METHODS: Total 538 mouse embryos(One, 2, 4, 8-cell, blastocyst, each 151, 136, 101, 98, 52, respectively) were cryopreserved and thawed using 1,2-propanediol and glycerol as cryoprotectant with slow cooling and rapid thawing technique, and compared the recovery, cleavage, blastocyst development rate, and calculated the recovery and reexpansion rate in blastocyst cryopreservation. RESULTS: Highest recovery, cleavage and blastocyst development rate were obtained from one cell, 8-cell stage freezing, 90.1%, 89.5% and 76.7%, respectively. In recovery rate, there was no significant difference among developmental stage, but in cleavage rate, there was significant difference between 2 and 8-cell group(p<0.05). In blastocyst development rate, there was significant difference between 2 and 8 cell, 4 and 8-cell group(p<0.05). Recovery and reexpansion rate of frozen-thawed blastocyst was 73.1%, 52.6%, respectively. CONCLUSIONS: Eight-cell embryo may be the best developmental stage for cryopreservation and blastocyst freezing also may be the promising technique.