Despite limited data, safety outcomes are reassuring.
There are two major factors limiting our current understanding of egg cryopreservation outcomes. First, many women who have cryopreserved their eggs haven’t used them, yet. Second, the babies that have been born have not yet reached ages where success can be properly evaluated. Despite these limitations, preliminary studies have been reassuring.
So far, studies have shown there to be no difference in the incidence of chromosomal abnormalities, no increase in the risk of congenital anomalies, and no increased risk of congenital anomalies or difference in birth weights.
In one study, a significantly higher rate of spontaneous abortions at 12 weeks or less was observed in the frozen/thawed oocyte group. Interestingly, in the group of 63 women who had pregnancies derived from both fresh and thawed oocytes, no differences were noted in the abortion rate or mean birth weight.
When should we freeze eggs?
Women decide to freeze eggs for a variety of reasons, and typically we divide those reasons into two categories: medical or social. Medical egg freezing is when there is an immediate medical threat, such as before starting cancer treatment. Social freezing is when there is no immediate medical threat, but the person is motivated by external factors such as a desire to delay parenthood to pursue educational or professional goals.
The difference is important in that groups of people find themselves divided ethically and politically about the acceptability, and insurability, of each type.
Is the cost worth it?
A major issue for women, especially for those considering egg freezing for social reasons, is whether the process is able to provide a fair chance for pregnancy later when they are used. Not all eggs survive thawing after vitrification, and of those that survive, not all will become fertilized. Only about half of fertilized eggs grow to a day 3 embryo, and not all of those embryos will be viable. Constant reproductive loss occurs after the eggs are retrieved.
What is the probability of a live birth?
A 25-year-old woman with 12 eggs frozen would have an estimated pregnancy rate much greater than 50%. However, egg freezing as it is today is not very successful for older women who, at this time, constitute many of those considering the procedure.
We have seen great strides taken in fertility treatment over the years, and it will be interesting to see where science and new technologies can take us next.