Experience suggests that there are three main risks associated or potentially associated with the hormone treatment used in ovarian stimulation: ovarian hyperstimulation syndrome, cancer, and effects on future fertility. Each risk has its own characteristics and its own implications for egg donors.

To understand the potential risks associated with the hormone therapy used in egg donation, one must first understand the hormone therapy itself. And that, in turn, requires an understanding of how the body produces eggs, without outside intervention from administrated hormones.

When a baby girl is born, her ovaries contain roughly 2 million oocytes, each encased in a protective covering called a follicle (see Figure 2-1). At this point, all of the follicles are primordial follicles—follicles that have not taken the first steps down the developmental path that leads eventually to mature follicles. And each of these primordial follicles will sit dormant in a woman’s body for as long as 50 years or more, waiting for a signal—researchers are still not sure exactly what that signal is—that will cause that follicle to leave the primordial pool and begin slowly to mature.

Whatever that trigger is, throughout a woman’s life there is a steady exodus of these follicles from the developmental pool and down the developmental pathway that will lead eventually—if the follicle survives—toward maturity and ovulation. But only a very few survive, as noted at the workshop by Nicholas Cataldo, formerly an assistant professor of obstetrics and gynecology at Stanford University School of Medicine. At the time of a woman’s first menstrual period, she still has 400,000 or so of these primordial follicles, and by the time of menopause they are almost all gone—indeed, it is their absence that triggers menopause—which implies an average attrition of about 1,000 follicles a month. That attrition, Dr. Cataldo said, can occur anywhere along a follicle’s developmental path, from its first step as a primary developing follicle, through its secondary follicle stage, and on to its final stage as an antral follicle. It is the antral follicle that, under the influence of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), will grow into a large mature follicle with a mature oocyte in its fluid core.