Effects of in-vitro fertilization, culture, freezing and transfer on the ability of mouse embryos to implant and survive

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Abstract
The survival after transfer of frozen-thawed mouse blastocysts obtained from culture of in vitro fertilized oocytes or 1- and 2-cell ova was compared. Abount 10% of transferred embryos developed to term in each group and there was no difference between embryos fertilized in vitro or in vivo. In addition to embryonic loss due to transfer, in vitro cultivation and freezing reduced the proportion of fetuses considered viable at day 15 of pregnancy (29.8 vs. 50.7% and 26.3 vs. 50.7%, respectively). When used together these procedures had an additive effect on fetal wastage (18.4 vs. 50.7%). In vitro culture also entailed a significant increase of resorbing implantation sites (10.2 vs. 4.3%). The reexpansion rate after freezing and thawing of blastocysts grown in vitro was paradoxically greater than that of blastocysts grown in vivo (85.8 vs. 54.6%).