I was recently updating some friends about our time in Victoria and one of them was pondering exactly how it is that the embryos are frozen without damage. This too got me curious, so I did a little reading and thought I'd share this fascinating, scientific part of this process.
In basic terms, embryo cryopreservation that is practiced today is done using a technology called vitrification. As we know, cells are primarily made up of water so the biggest threat of freezing them is the formation of ice crystals. Vitrification can be thought of like "flash freezing". According to the VFC website,
The embryos are plunged into liquid nitrogen at around minus 200 degrees. The liquid therefore does not have time to form crystals and assumes a "glass like" state. Therefore there is no damage caused by ice crystals.Crazy!
I did some more digging about embryo survival rates after freezing and thawing and found a lot of statements similar to this one:
Vitrification provides a higher survival rate, minimal damaging effects on embryo morphology after thawing/warming and it can improve clinical outcomes (when compared to the previously used technology of slow freezing).For those who like numbers, I saw some stats that put the survival rate for embryos frozen on Day 3 (our case) using slow freezing around 70% and vitrification closer to 85%.