A woman’s ovaries are the site of far more death than life. The destruction begins even before a baby girl has emerged from her mother’s womb. A human female embryo develops around 7 million proto-eggs, known as primordial oocytes. By the time she is ready to enter the world, no more than 2 million are left alive, the rest having fallen prey to a mysterious process of cellular suicide, one that will continue to claim oocytes as the girl grows. By puberty there are at most only a quarter of a million oocytes left. In a woman’s lifetime perhaps 400 will become full-grown eggs capable of being fertilized by sperm.
The remaining oocytes continue to die off until menopause, when virtually none are left. The mature egg cell, observes Roger Gosden, a reproductive biologist at the University of Leeds in England, is the rarest cell in the human body.
The situation is decidedly sexist. A male’s single ejaculation contains in the neighborhood of 200 million sperm, and most men go on creating new sperm long after they start cashing Social Security checks. Not surprisingly, this imbalance has made itself felt in the fertility business. Sperm banks have become so commonplace that firms have to jockey for business. When it comes to eggs, though, the success of in vitro fertilization has created a demand far exceeding supply. Disease, sterilizing cancer therapy, and advancing age can leave women incapable of providing themselves with viable eggs; if they want to bear children, they must resort to eggs donated by other women. Unlike sperm, mature eggs are almost always ruined if they are frozen, so there are no egg banks; instead clinics have to advertise for volunteers continually.
In the United States those voluntary donors receive several thousand dollars for each harvest of eggs, and it is hard-earned pay. They must inject themselves daily for four weeks with large doses of hormones to encourage their ovaries to produce numerous mature oocytes while simultaneously suppressing the normal menstrual cycle, which would eject the eggs into the fallopian tubes. This regimen can produce ovarian cysts, headaches, nausea, and bloating. According to some controversial studies, it can even increase the risk of ovarian cancer, and the hormone injections can, on rare occasions, cause a potentially fatal condition called ovarian hyperstimulation. Donors must regularly undergo ultrasound and blood tests to monitor their developing oocytes. The process ends with major surgery, complete with general anesthesia, as a surgeon pierces a donor’s vaginal wall with a needle and sucks the eggs out of the ovaries.
