Egg freezing also known as oocyte vitrification, is a fertility preservation technique that enables women of delaying motherhood for the future to all women who want to do so for various reasons, social or medical. It can be achieved if the eggs are congealed from an early age where the fertility potential is upper.
Vitrification is a flash-freezing process where a liquid is transformed into a highly viscous solid with a glass-like consistency. The advantage of this technique over slow-freezing procedures is its rapid cooling rate, which prevents the formation of ice crystals that can harm the egg by damaging cell structures. Although this technique was discovered more than 60 years ago, it wasn’t until a few years ago that it was modified for assisted reproduction in humans by the Japanese group, Kuwayama, using the Cryotop system; it is now used regularly in a large number of assisted reproduction clinics around the world. Although there are numerous devices on the market, Cryotop is the best technique currently available and therefore the best option for creating oocyte banks.
The Treatment – Step by Step
Who is it recommended for?
Women could take advantage of this method especially when they present ovarian failure or precocious menopause and they need to resort to egg donation. The establishment of donated eggs banks will simplify the logistics of this procedure. These banks could provide immediately eggs for women that require them, compatible with the couple and at the same time eliminate the problem of the waiting lists.
Finally, the egg freezing would avoid in many cases the ethical and moral prejudices that the freezing of embryos entail for many couples.
In this sense, the cryoconservation of gametes does not represent any type of worry, reason why it is possible to fertilize the suitable number that allows the transference of a maximum of 3 embryos, according to the Law on techniques of assisted human reproduction.
What is the procedure?
This procedure follows the same steps as in an In-Vitro Fertilisation (IVF) cycle: ovarian stimulation with hormones, oocyte aspiration, and instead of inseminating and fertilising them, they undergo vitrification (Cryotop method) before storing them in liquid nitrogen.
The oocytes can be cryopreserved for as long as the patient wants or needs, there is no time limit on this. With the Cryotop technique we have achieved survival rates of up to 97% in young patients (under 35), and pregnancy rates similar to those obtained with fresh oocytes.
The main factor that negatively affects survival rates is maternal age, although the results are similar to those obtained with oocytes before vitrification. No differences have been observed in the birth weights of live born babies when compared to those obtained with fresh oocytes in both single and twin pregnancies.
Oocyte vitrification for patients with cancer
Women with cancer and high life expectancy, regardless of their age, need to preserve their reproductive potential when facing cancer treatment, a potential cause of infertility. For these women, the option to freeze and store their eggs in an egg bank could save their reproductive potential and allow them to become pregnant in the future.