Egg Cryopreservation
Despite the demand for it, egg cryopreservation is not performed nearly as often as sperm and embryo freezing. Why? Because freezing and thawing female eggs is a much more delicate procedure; one that is only beginning to be done successfully.
What is Cryopreservation?
Often done for sperm and extra embryos produced during IVF, cryopreservation is the process of freezing materials so that they can be used at a later time. Cryopreservation is a fairly simply process usually involving liquid nitrogen to freeze the sperm, embryos or eggs. These materials are then stored in special freezers until they are needed, which can be anywhere from months to years after they are frozen.
Why Not Eggs?
Officially known as oocyte cryopreservation, freezing eggs is a much more difficult procedure than freezing either sperm or embryos. Women’s eggs are made up of tissue that is much more delicate and likely to be damaged during the thawing process. Unlike sperm, which are small cells with a low water content, a woman’s eggs are fairly large cells with a high water content. As a result, your eggs are more susceptible to forming damaging ice crystals during the freezing process which can make fertilization at a later date nearly impossible.
Another issue with freezing eggs is the quality of the eggs. Because female egg quality declines with age, the older the woman, the poorer health her eggs are likely to be in. Since an egg already has a high chance of being damaged during cryopreservation, freezing eggs that are likely to be in poor health only serves to further decrease your chances of successfully becoming pregnant later. Moreover, an older woman may not be able to produce enough quality eggs to make cryopreservation worthwhile.
How is Egg Cryopreservation Done
Freezing eggs is a rather involved process. First, you are given injectable fertility drugs (gonadotropins) daily to stimulate your egg production. Just before you are set to ovulate, your eggs will be retrieved in the same type of procedure that is used for IVF. Once the eggs have been harvested, they will be frozen with liquid nitrogen and stored in special freezers until you decide to use them. A newer technique that is still being tested involves flash-freezing the eggs.
While the majority of the process is still the same, your eggs are instantly frozen rather than slowly frozen. The main benefit to this process is that it avoids the formation of ice crystals. As a result, the eggs can be thawed with virtually no damage done to them thus improving your chances of conceiving and having a successful pregnancy. However, flash-freezing eggs has been shown to make conception through IVF more difficult. Therefore, it is often necessary to use ICSI in order to fertilize the egg.
Iit is still unclear just how long female eggs can safely be stored before they are no longer viable for treatment.
Am I a Candidate?
Initially, egg freezing was mainly offered to women who were undergoing cancer therapy or treatment for some other form of illness that impacted their ovarian function. Since many medical treatments can cause infertility, egg cryopreservation was one way to preserve a woman’s fertility.
Overtime, though, more clinics began to offer this service. Nowadays, most women, at least those living in the United States, can have access to this technology. As a result, women who are still young and healthy but know that they would like to wait until they are in their late 30s before starting their families have also begun to take advantage of this technology. Women who are older than 35, though, are usually encouraged to consider egg donation rather than freeze their own eggs.
Other people who may choose egg cryopreservation include individuals who are opposed to freezing embryos.
Costs and Alternatives
Egg cryopreservation does not come cheaply. Depending on the fertility clinic you attend, freezing your eggs can cost as much as $12,000 and possibly even more. While this covers your consultation, ovulation medications, cycle monitoring and retrieval of your eggs it does not cover storage, thawing or the cost of IVF and ICSI. The final price tag on the treatment is likely to be close to $20,000.
Due to the large costs associated with the procedure, and considering that experts have still not developed an effective and efficient way to freeze and thaw female eggs, women are often encouraged to consider female egg donation instead.
Many researchers are also pointing out that cryopreservation of embryos, as well as ovarian tissue, may be a more viable option for women to produce biological children at a later age. Both embryos and ovarian tissue have been shown to freeze and thaw much better than female eggs.
Others have suggested retrieving the eggs just prior to maturation (about one or two days before you would normally ovulate) as these eggs are not as easily damaged in the freezing process. However, eggs that are not fully mature are often harder to fertilize thereby increasing the chances of the procedure being unsuccessful.
Currently, flash-freezing holds the most promise for making egg cryopreservation a common reality for women. While significant advances have been made in this area of research, more work is still needed to ensure the efficiency of the procedure.
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