What is it like?
In order to have high survival rates, the oocytes must be frozen using certain methods and means. Otherwise, ice crystals would form, which would eventually damage the cell structure and its organelles, since 70% of the cell’s composition is water. It is the same phenomenon that happens when you freeze a glass bottle of water. Accordingly, a special technique is necessary to achieve to achieve the correct cryopreservation of the eggs.
Years ago, the freezing technique in the assisted reproduction laboratory was slow freezing, which quite easily formed ice crystals that ended up damaging the eggs. Survival rates were not very high with this technique. Currently, advances have been developed that allow the use of an ultra-rapid freezing technique, or vitrification, which avoids the formation of crystals. This is achieved by immersing the oocytes in cryoprotective means (which protect them from freezing) and then cooling them in very small volumes rapidly and at extremely low temperatures by placing them in liquid nitrogen at -196ºC.
With this technique, however, the amount of cryoprotectants (substances that protect against freezing) used is greater, and therefore the exposure time of these with the cells must be very controlled so that they do not damage the cell. It is very important to carry out a correct control of this process.
This procedure guarantees a high survival of the eggs when thawed, between 90-95%. This means that with in vitro fertilisation the results are very similar to those obtained with fresh eggs (not vitrified).