Survival of thawed embryos

Not all embryos have the same ability to survive the freezing-thawing process and about 20-30% of their cells are destroyed. However, it has been proven that embryos that successfully survive after thawing have the same implantation potential as fresh embryos, and sometimes even higher, due to a better implantation window.

Frozen-thawed Day-3 embryos with excellent survival.

Frozen-thawed Day-3 embryos with excellent survival.

The damage of one or two blastomeres in a day 3 embryo does not impair successful implantation. At this stage the cells are still totipotent, i.e. they have not been differentiated yet. There are reports of live births following transfer of thawed embryos that had lost 7 out of 8 cells.

In addition, there are reports of live births in cases when frozen-thawed embryos, were re-frozen as supernumerary, showing that cryopreservation does not seem to affect the chromosomal status of an embryo.