How long can my eggs remain frozen without damage?

Once we have vitrified the oocytes, they do not deteriorate over time. They remain in exactly the same condition as when they were vitrified, which means they can be frozen indefinitely.

1. Is there a maximum time limit for storing frozen eggs?

There is no time limit as such. It is reasonable to store them for as long as the woman wishes and provided that their use is reasonable, i.e. provided that the woman who is going to use them remains in good health to be able to carry a pregnancy, but there is no expiry date as such for frozen eggs.

2. Why do eggs not deteriorate while frozen?

The technique used in laboratories today (vitrification) involves storing oocytes at very low temperatures, in liquid nitrogen at -196ºC. This allows cellular activity to stop completely.

3. Does the length of time they are frozen affect the chances of pregnancy?

No, the length of time they remain frozen does not affect your chances of success. The most important factor is the age of the woman when they were vitrified.

4. What determines the quality of the eggs after thawing?

Once again, age at the time of vitrification is the most important factor, as the loss in egg quality is more noticeable as the age of the egg increases. We see how, as age increases, survival rates after thawing worsen.

The experience of the embryologist performing the vitrification technique in the laboratory is also important.

5. What happens when a woman decides to use her frozen eggs?

Once we have carried out the necessary preliminary medical evaluation, the endometrium is prepared to receive an embryo. At the same time, biologists proceed to thaw the oocytes and perform the in vitro fertilisation technique known as ICSI (Intracytoplasmic Sperm Injection). From there, embryo culture begins, which normally lasts 5-6 days, after which an embryo can be transferred to the uterus and any remaining embryos can be vitrified.

Dr Alicia Herencia, gynaecologist at Instituto Bernabeu Madrid and coordinator of the Specialised Oocyte Cryopreservation Unit.