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Assessing the Medical Risks of Human Oocyte Donation for Stem Cell Research: Workshop Report
THE RISKS OF OVARIAN STIMULATION
In order to increase the number of eggs that can be retrieved from a single donor, the donor normally takes a regimen of hormone shots, that is, fertility drugs. These hormones will generally cause 10 to 20 eggs—instead of the usual single egg—to mature in the ovaries at the sametime. The drugs also have a variety of potential health effects, some minor and some potentially major.
The most prominent side effect of this ovarian stimulation is ovarian hyperstimulation syndrome (OHSS). Its symptoms include increased ovarian size; nausea and vomiting; increased permeability of the blood vessels, leading to an accumulation of fluid in the abdomen; breathing difficulties; hemoconcentration, or an increased concentration of red blood cells; kidney and liver problems; and, in the most severe cases, blood clots or kidney failure. Data from women taking fertility drugs in order to undergo in vitro fertilization (IVF) show that only a very small percentage—about 0.1 to 0.2 percent—experience what is classified as severe OHSS, and a much smaller percentage suffer truly dangerous complications. For example, about 1.4 of every 100,000 women undergoing an IVF cycle experience kidney failure.
The OHSS risks for egg donors are expected to be much lower than the OHSS risks calculated from women involved in IVF. The reason is that a large percentage of the severe complications of OHSS seen in IVF patients are linked to hormonal changes in a woman’s body that accompany pregnancy. Since oocyte donors do not get pregnant in the cycle in which they donate their eggs, they can be expected to have many fewer side effects than IVF patients.
There is also concern that the use of fertility drugs may lead to an increased risk of hormone-dependent cancers—in particular, breast, ovarian, and uterine (endometrial) cancers. Epidemiological studies of this issue must be interpreted carefully, because infertile women generally are at higher risk for these cancers than women in the general population, so the increased risk due to infertility must be separated from any possible increased risk caused by fertility drugs. The evidence to date is limited, but does not support a relationship between fertility drugs and an increased prevalence of breast or ovarian cancer. More research is required to examine what the long-term impact fertility drugs may be on breast and ovarian cancer prevalence rates. For uterine cancer, the numbers are too small to achieve statistical significance, but it is possible that fertility drugs may cause some increased risk of uterine cancer.