In 1972 preimplantation
mammalian embryos were successfully cryopreserved.
The method was very time consuming. Slow cooling (1 degree/min
or less) to about -80 degrees Centigrade. The embryos were then
placed in liquid nitrogen. Also, the embryos needed to be thawed
slowly and cryoprotent added and removed in many small steps.
This was a lot of work.
The first reported human pregnancy from frozen embryos was reported
in 1983 by Trounson and Mohr.
Most of the research has been done on mouse embryos. Development
of frozen thawed mouse embryos, in vitro and in vivo, is not statistically
reduced as compared to their non-frozen controls. This is not yet
true for any other species.
Information excerpted from Advanced Fertility Center Chicago, IL