Everyone (almost) has heard about sperm banks and the opportunity for men to either sell or save their sperm for use at a later date. It has been an established ‘fact’ for many years that the age of a woman’s egg can contribute to birth defects, especially Down syndrome. Tests can now be performed on a pregnant woman who is approaching middle age to determine if her fetus does have any birth defects. However, of late there has been some murmuring in the medical community that the age of the sperm donor can also contribute to an unhealthy baby.
Today’s woman is very different to the woman of the early 1900’s. The modern woman sometimes wants it all but wants it all at different times in her life. Many career women are foregoing childbirth until later in life when there is greater risk for a healthy baby. Some women who can afford the procedure are opting for cryopreservation of her eggs while she is still in her twenties. Then, when she is in her mid to later thirties, she can use her own eggs for fertilization. This gives the woman the choice of bearing a potentially healthy child with or without a husband.
The largest published study of 900 babies from frozen eggs showed no increased rate of birth defects when compared to the general population. Additionally, results from one study showed no increased rates of chromosomal defects between embryos derived from frozen eggs compared to embryos derived from fresh eggs. There have also been over 300,000 children born worldwide from frozen embryos using primarily slow-freeze cryopreservation techniques without an increase in birth defects. Although these data are reassuring, it will take many years of follow-up to ensure that babies born from egg freezing technology have no higher rates of birth defects than those conceived through other means.
Fertility preservation through oocyte (egg) freezing allows women to store eggs at a younger age for use when they are older and is now a viable option for family planning. Whether eggs are being cryopreserved as a medical emergency in the setting of a newly-diagnosed cancer or for personal reasons, the technology holds great promise for women of reproductive age. To date, there are over 2000 births worldwide (greater than 1000 reported in the last five years) as a result of egg freezing.
The process involves stimulating eggs in the woman's ovaries and then harvesting and storing those eggs for use at a later date. Oocyte quality is best when a woman is in her reproductive prime (age 16 to 28). Many eggs are usually still of good quality in the mid-reproductive years (age 29 to 38) and may remain usable (but with diminished chance for producing pregnancy) in the late-reproductive period (age 39 to 44). If necessary or desired, it is best to have eggs that are frozen when they are of the best quality possible. For instance, eggs frozen at the age of 35 are more usable than fresh oocytes produced at 43 years of age.
Egg thaw rates of 75% and fertilization rates of 75% are anticipated in women up to 38 years of age. Thus, if 10 eggs are frozen, 7 are expected to survive the thaw, and 5 to 6 are expected to fertilize and become embryos. Usually 3-4 embryos are transferred in women up to 38 years of age.
It is important to know that the timing of egg freezing treatment is, in part, determined by the internal reproductive hormones and that the treatment cycle is generally started at the beginning of the menstrual cycle. One oocyte cryopreservation treatment cycle takes about two weeks to complete and, during that period, the woman’s schedule needs to be relatively flexible. She needs to be available for frequent morning monitoring of the egg development and for the oocyte harvest procedure. Travel should be limited during the treatment cycle and she should be aware that the exact days treatment will occur cannot be determined ahead of time. In fact, the body's response to the fertility medications controls much of what happens in the process.
Expectations are that pregnancy rates from frozen eggs will depend on the women’s age at the time she freezes her eggs, but will not be affected by the age at which she comes back to use them. Therefore, the chance of future pregnancy in women older than 38 at the time of freezing is likely to be lower than that seen for younger women. To date, there are few reports of pregnancies in women over 38 from frozen eggs. This is mostly due to lower age cutoffs in egg freezing studies and the relatively low number of women who have come back to use their frozen eggs.
Some fertility clinics and physicians consider this new-age development as an ‘experimental’ procedure – but not all. It is not an inexpressive process and can cost almost as much, if not more, than a legal adoption. To mitigate chances of losing a good deal of money in the process a test for levels of anti-Mullerian hormone can help predict whether doctors will get enough eggs to make the procedure worthwhile.
