Most of us learned in our high school health classes that we women are born with a lifetime supply of eggs in our ovaries that drastically diminishes throughout our childhood and reproductive years. But yesterday's news suggesting that female ovaries may indeed be able to churn out new eggs could provide hope for those women who find they don't have enough healthy eggs left when they're ready to have a baby. Chinese researchers extracted stem cells from the ovaries of mice and demonstrated that the cells gave rise to new eggs and that healthy babies could be produced from those eggs. Note: These female germline stem cells were taken from adult mice and weren't embryonic stem cells.
As exciting as the study is, its results are a far cry from demonstrating that such a technique can work in women. If it does, though, it could solve a lot of fertility problems. Many women undergoing cancer treatments are rendered infertile from egg-destroying radiation and chemotherapy. While freezing eggs prior to therapy currently gives many women the chance to have a child in the future, many doctors fail to discuss it until after treatment begins and it's too late.
What's more, freezing eggs is far more complicated than freezing sperm. Egg membranes are very delicate and can easily disintegrate if the freezing isn't done properly. Researchers have reported that only about half of eggs are viable after thawing, but this can vary from woman to woman, with 90 to 100 percent survival in some and 0 to 10 percent in others, according to one infertility website. And no one really knows how long frozen eggs can remain viable. Doctors have far more practice using thawed sperm or thawed embryos to create babies, while working with previously frozen eggs is still relatively rare.
The stem cell technique could also hold promise for women who delay childbearing until their eggs are too old. For many, this occurs in their late 30s, a decade or more before menopause. Currently, these women try in vitro fertilization—often unsuccessfully—using whatever viable eggs doctors manage to extract from their ovaries, or using a donor egg, which is difficult to obtain. Some choose to adopt rather than go through the costly medical interventions. If the new technique is found to work in women, using it would involve simply removing a sample of stem cells from the ovary, growing them into eggs, and implanting those eggs back in the ovary so that a woman could get pregnant the natural way.
There are, however, quite a few unknowns. Do female germline stem cells exist in the human ovary? Do these stem cells exist regardless of a woman's age? Even after cancer treatments? Can they be coaxed to produce viable human eggs? Could a woman who has new eggs implanted ovulate on her own and become pregnant? Would the babies produced from these eggs be completely healthy?
If and when these hurdles are overcome, we then have to worry that the technique could be misused in older women well beyond menopause. There have been occasional reports of 70-something women giving birth through in vitro fertilization. So I cringed when I read a British headline yesterday declaring that the new technique may "allow women to delay menopause." Like other fertility treatments, this one, if it's shown to work, has the potential for widespread abuse.