Retrieval of ripe eggs versus in-vitro maturation (IVM)
Since the development of an advanced freezing technique, referred to as 'vitrification' it is possible to freeze eggs. It has enabled the CRG to set up an egg bank similar to the sperm bank.
When eggs are frozen, their biological clock is put on hold: they don't continue to age and cannot be damaged by external factors. Freezing eggs offers women the opportunity to keep their reproductive potential without the need for fertilisation first (to freeze embryos).
Freezing eggs may offer a solution to different groups of women:
- women can have their eggs frozen before starting treatment that may damage their ovaries (such as chemotherapy), particularly young women who don't have a partner yet;
- women who want to donate eggs;
- women who want to use donor eggs;
- single women who have not yet found a partner with whom they want children;
- women (in general) who want to delay having children.
Particularly for egg donation
, the existence of the egg bank has been a massive bonus: egg donation with frozen/thawed eggs is more efficient and patient-friendly. The egg donor also enjoys greater freedom in planning her treatment, because we don't have to take into account the preparation of the recipient.
Practically all egg donations involve the egg bank for this reason.In-vitro maturation of immature eggs
Normally speaking, to freeze eggs you need to follow the part of the IVF treatment required to stimulate and collect different follicles: ovarian stimulation
and egg retrieval
Now there is also a more patient-friendly alternative: the collection of immature eggs which are matured in the laboratory. This is known as IVM or in-vitro maturation.
The immature eggs can come from:
- an 'ordinary' egg retrieval, even if this only requires light stimulation;
- from ovarian tissue – e.g. as a result of an ovariectomy prior to cancer treatment.
Ovarian tissue that needs to be frozen and stored undergoes a number of procedures in the laboratory first. During this process, immature egg are usually released. These immature eggs cannot be used but thanks to IVM they can be matured and stored.
IVM is an advanced technique, which is considered safe, and is being used with increasing success: worldwide already more than 5,000 children have been born after retrieval of immature eggs followed by IVM and in-vitro fertilisation in couples with reduced fertility.