Embryos freezing by vitrification
When you undergo an in vitro fertility treatment, the number of embryos that develop may be higher than those you need to use in the transfer. In this cases, the embryos left can be cryopreserved in the embryos bank to be used later on in another transfer, in the event of wanting to increase the family. They can also be donated to other couples with fertility problems that want to opt for adoption to be parents.
Even though freezing the embryo may decrease somewhat their viability, our percentage of pregnancy with embryos thawed is increasingly similar to the transfers with fresh embryos. This is because we use a freezing technique called vitrification which has a great advantage, over the conventional freezing method, of obtaining better surviving results in thawed embryos. It greatly improves the pregnancy rate and resembles to the transfer of fresh embryos surpassing the 40%.
If we compare vitrification with the classical freezing method, vitrification cools the cells in a very fast way, at a speed of more than 15.000ºC per minute. This avoids the formation of ice particles from the water they contain and that would harm the embryo. The vitrification forms a sort of gel that doesn’t harm the cells and therefore significantly increases the chances of success.
Our success rate on embryo vitrification can be higher than a 40%; a percentage similar to the one obtained with fresh embryos transfers. The HLA Vistahermosa Reproduction Unit is one of the centres in Spain to first abandon, years ago, the classic freezing method to only use the vitrification of embryos.