Freezing IVF Eggs
The procedure for freezing and storing eggs from a woman's ovaries is called oocyte (egg) cryopreservation. It is notoriously difficult to do successfully, but nonetheless, some women want to give it a try for personal or medical reasons. Egg freezing can be carried out in conjunction with a cycle of IVF treatment. If, thanks to ovulation-inducing IVF drugs, more eggs than are needed for one cycle are harvested from the ovaries, these eggs can be preserved for later use.
How Is It Done?
Freezing eggs is a lot harder than freezing sperm or even embryos (eggs which have already been fertilized by sperm). This is because the egg is mostly made up of water, which can easily crystallize during the freezing or warming-up process. This can damage the egg. Only around 100 live births have been reported worldwide in which the baby was conceived using an egg that had been frozen. At the moment, oocyte cryopreservation is available at only a limited number of fertility clinics.
With the chances of success being so low, you might ask why women would choose this option, given that freezing embryos is easier. There are in fact many reasons why a woman might decide to freeze her eggs.
For example, she might be in a relationship but, nevertheless, she wants to delay pregnancy for career or other personal reasons, with the option of becoming a mother later on. On the other hand, she may be in her mid- to late thirties with no potential father on the horizon, and therefore she wants at least to have the possibility of having her own child with him when he finally shows up, or with a sperm donor if he doesn't!
If a couple is going through IVF treatment to get pregnant, but the woman is very sensitive to the drugs, and is susceptible to OHSS (ovarian hyper stimulation syndrome), it may not be safe for her to do another cycle if she doesn't get pregnant first time around. In a situation like this, it might be preferable for her to freeze the excess eggs harvested in the first cycle, to avoid having to take ovulation-inducing drugs in the next cycle.
If a woman knows that she is going to undergo treatment for cancer (chemotherapy), which can lead to permanent infertility, she may want to have her eggs preserved before the treatment begins.
Lastly, a couple, for religious or ethical reasons, may be opposed to freezing embryos which may later be discarded (if they consider the embryo to be a human life already). Such couples may prefer to freeze the male partner's sperm and the female partner's eggs in anticipation of future fertility treatment.
There are hopes that a rapid freezing process called vitrification will lead to improvement in the survival rate for frozen eggs. In this process, the eggs are cooled very quickly by, for example, surrounding them with liquid nitrogen. The eggs then freeze to a semi-solid state without any crystallization.