The cryopreservation of oocytes, the way to ensure their fertility

Freezing ovules is a good way to ensure your fertility in the future. It is indicated for women who, for economic or social reasons, must postpone their maternity and for patients who are going to receive medical treatments that can damage the oocytes.. This technique represents a great revolution in assisted reproduction .

What is the cryopreservation of oocytes?

The cryopreservation of the oocytes is the freezing of the female gamete with the intention of using it later. The technique must ensure that the gamete does not lose fertile potential, that it is capable of thawing afterwards, to give rise to embryos that are viable and that give rise to normal pregnancies and healthy newborns.

When is this technique indicated?

This technique opens a window of hope for the fertility of many women. The first indication is for those patients who, for social or economic reasons, have to postpone their maternity wishes and want to safeguard their fertility by freezing oocytes that will later be useful.. It is also especially indicated in patients who will then receive medical treatments that could damage the oocytes, and before they are damaged they can be frozen for later use. This technique also opens up the possibility of creating oocyte banks that will be very useful both in oocyte donation programs and for cloning programs for non-reproductive purposes for cell therapy and tissue therapy.

How is cryopreservation of oocytes carried out?

There are two procedures for freezing oocytes, slow freezing and ultrafast freezing or vitrification. Currently vitrification is used, which consists, in a first step, exposing the oocyte to a hyperosmolar solution with which we get to dehydrate it and then an ultrafast freeze. With these two procedures it is possible to avoid the formation of intracytoplasmic crystals that could damage the oocyte .

What risks can we find in the cryopreservation of oocytes?

The risks are derived from the technical procedure used. We have commented that the oocyte must be subjected to a hyperosmolar solution to dehydrate and, it is known that these solutions can cause damage to the oocyte, as well as the freezing process itself, which can also cause damage to the oocyte.. That is, we have the toxic effects of the cryopreservation substances that are used and the very phenomenon of vitrification. The most known damages are those that occur at the level of meiotic use and those that occur in the cytoplasmic or oocyte corpuscles. The latest work done shows that with new cryopreservators and vitrification techniques these damages are no longer occurring.

What results can be expected with this technique?

In the beginning, the doctors who used these techniques were very cautious, there was not enough evidence about the nature of the pregnancies that were going to be achieved using devitrified oocytes. With the last few years we have seen that ovulation devitrification leads to a very high ovocyte survival rate, of the order of 97%, fertility rates, implantation rates, pregnancy rates and "baby at home" rates, quite similar to those that are produced with fresh oocytes. That is why this technique has been an important advance in all assisted reproduction programs.