Mouse blastocyst vitrification compared with the conventional slow-freezing method.

To compare mouse blastocyst survival after cryopreservation with vitrification and the slow-freezing method, one-hundred and forty-eight in vitro mouse blastocysts were randomly frozen by the two methods: vitrification and conventional slow-freezing. After being thawed, the blastocysts were assessed for survival and hatching rate. The survival rates of blastocysts cryopreserved by vitrification and slow-freezing were 68.33 and 65.52 per cent (p = 0.89), whereas hatching rates were 51.22 and 44.74 per cent, respectively (p = 0.64). Therefore, vitrification of blastocyst-stage-embryos may be a useful, economic method for freezing the excess blastocysts in some centers where blastocysts are routinely transferred.