Fertility preservation is not something new as different techniques have been used to try to prevent the passage of time from affecting the chances of a woman to conceive with her own eggs. But this is something not well known at the very moment when we could do it, but it is learnt later, when it may be too late for fertility preservation.
There are two main indications for fertility preservation. The medical indication, when someone must undergo an aggressive medical treatment that may affect his/her reproductive capacity after treatment. And the social indication, in which someone decides to postpone fertility for work, social, economic reasons …
In case of men, fertility preservation is accomplished by freezing one or more sperm samples, that can remain frozen until the male decides either to use them or to destroy them.
For women, there are two main possibilities for fertility preservation. The first one is the preservation of ovarian tissue, which is carried out mainly for medical reasons and in adolescent and pre-adolescent women, to avoid ovarian stimulation. The second one, and more frequently performed, is the preservation of oocytes through their vitrification.
Egg preservation is achieved by their vitrification or, what is the same, their maintenance at -196º in liquid nitrogen. Under these conditions, oocytes maintain their development capacity after devitrification by 95%, allowing a woman to have her eggs for the future, without them having suffered the negative effects of the passage of time.
But make no mistake, oocyte vitrification will be all the more effective the better the quality of the oocytes, for which age is a determining factor and so, after 35 years the chances of success decrease. Thus, there is no clear age limit to be able to preserve the oocytes, but it is true that the older the age of the woman, the lower the possibility of vitrifying good quality oocytes and therefore the lower probability of pregnancy with these oocytes in the future. The same happens with the number of vitrified oocytes, there is no magic number that guarantees pregnancy. In fact, no number of oocytes offers a guarantee. But it is true that some studies suggest that between 15 and 20 oocytes could allow a pregnancy in the future, with an 80% probability for women under 35 years of age.