[Comparison of vitrification cryopreservation among different stages of mouse embryos]

The cryopreservation of different embryo stages collected from ICR, C57BL/6 and F1 of DBA*C57BL/6 was carried out by using vitrification method. The morphology, in vitro development and birth rates of these embryos were compared after frozen-thawed. The results showed that more than 75% of the morphology from 2-cell embryos to morula stages from different strains was normal, the normal morphology rates of 8-cell embryos being the highest, while those of blastulas being the lowest. The in vitro development rates became higher as the embryos developed. The morphology of in vivo and in vitro fertilized frozen 2-cell embryos showed no difference, but the development rate of in vivo fertilized frozen 2-cell embryos was significantly higher than that of in vitro ones. Embryos that underwent 3 times frozen-thawing remained normal morphology. The pregnant rate and birth rate of frozen 2-cell embryos after embryo transfer were 64% and 40% respectively, but lower than those of fresh 2-cell embryo transfer.