Women May Have an Alternative to Freezing Their Eggs
Here’s how it could go: Some day in the future, it’s routine for every young woman of a certain age—for argument’s sake, let’s say 21—to undergo a procedure to snip off a piece of tissue from one of her ovaries. Her doctor slices up the tissue into a half-dozen or so microthin sections; these are frozen, to be used whenever she’s ready for a baby. Her ovaries function normally, and she keeps menstruating and ovulating just as she has since puberty. But she doesn’t worry about rushing into baby-making. The timetable of how her life unfolds need not adhere to a pesky biological clock.
Later, maybe much later, maybe not for another 20 years, this woman wants to start a family. She remembers those strips of ovarian tissue in deep freeze. Each strip contains thousands of follicles, the proto-eggs of the ovary, preserved at their peak. The follicles in her body have been getting progressively less robust, but in the lab freezer her proto-eggs have been in suspended animation, protected from the degradation of age.
So she goes back to the doctor, who defrosts one of the strips and implants it in her ovary. It becomes established there, starts pumping out hormones at the level of a younger woman, and transforms one follicle each month into a mature egg. Each menstrual cycle, the hardy egg of a 21-year-old is deposited into the fallopian tube, where it can be fertilized. Ideally, one of those youthful eggs turns into an embryo that embeds itself in the uterus and grows into a healthy baby. Ideally, that one strip of ovarian tissue keeps producing hormones and releasing eggs for years, long enough for the woman—who might be 45 or even older by the time it’s all done—to have a couple of children.
If the first implant doesn’t work, or if it stops working before the woman’s family is complete, doctors can defrost and implant another strip. And if she doesn’t need the strips for childbearing—maybe she decides not to have children at all, or she gets pregnant naturally without needing to take any strips out of deep freeze—she can use them for a different purpose: postponing menopause. As she enters her fifties, this woman thaws a strip and has it implanted in her forearm, where it releases estrogen and other sex hormones in a way that mimics the feedback loop of a younger woman, in theory with fewer side effects than with artificial hormones. She still menstruates, which is the downside, but she also remains at lower risk of chronic conditions, like heart disease and osteoporosis, that usually get worse after menopause, at least in part because of the drop in estrogen. In this future, the one-two punch of nature’s timetable—first making it harder to have healthy babies after about age 35, then making it harder to stay healthy yourself after about age 50—is something women have finally transcended.
Here’s the reality of where things stand: At the Center for Human Reproduction in New York, there’s a room with a boxy machine that slow-freezes slices of ovarian tissue before they are transferred to a stubby deep-freeze tank that bears an uncanny resemblance to R2-D2. But of the 14 tanks in the room, most contain frozen embryos or frozen eggs or sperm, not ovarian tissue. That’s because right now, removing ovarian tissue involves an expensive surgery requiring a hospital stay. (Infertile men can have a bit of testicular tissue removed via a comparatively simple probe-and-snip procedure; the hope is that a similar procedure can be developed for women.) Transplanting the tissue later requires another operation.
Which is all to say, we already do live in a world where bits of ovarian tissue can be harvested, frozen, and then reimplanted later to make a woman fertile, but it’s harrowing. The process was developed for young women or girls with cancer, who face oncological treatments that are certain to make them sterile; since 2004, about 100 babies have been born to these women using the technique. In the view of most researchers and the American Society of Reproductive Medicine, ovarian tissue extraction is still too experimental to recommend for healthy women.
But soon, say experts like Sherman Silber, director of the Infertility Center of St. Louis, freezing ovarian tissue could become the next big form of what’s known as “social freezing” (or, as it’s called in some waggish circles, “AGE freezing,” short for “anticipated gamete exhaustion”)—whereby women try to prolong their fertility not for a medical reason but just to give themselves the option of delayed childbearing. For now, the only way to pause the biological clock this way is to freeze one’s eggs, a route taken by some 6,200 women in the US in 2015. But egg freezing is expensive (up to $18,000 per cycle) and uncertain. Experts calculate that each egg frozen before age 38 has just a 2 to 12 percent chance of turning into a baby one day. Egg freezing also requires women to inject themselves with hormones powerful enough to produce more than 10 times the normal number of mature eggs at a time. These hormones can lead to mood swings, nausea, and abdominal pain; a slight chance of the serious condition known as ovarian hyperstimulation syndrome; and an unknown risk of ovarian or breast cancer down the road.
So as women wait longer and longer to have kids—more than 26,000 women 40 or older became first-time mothers in 2016, an increase of nearly 30 percent over 2001—there’s plenty of incentive for the fertility industry to figure out how to make ovarian tissue extraction a better bet than egg freezing. For one thing, it would do away with the need for multiple rounds of in vitro fertilization. If all goes well, Silber says, the thawed and transplanted tissue will latch on to the rest of the ovary, become functional within about four-and-a-half months, and lead to pregnancy the old-fashioned way.
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Roger Gosden, who helped develop the ovarian tissue-freezing procedure in sheep in the 1990s, worries that the social freezing of ovarian tissue will be fraught with the same hazards and anxieties as egg freezing: “A lot of commercial pressure and social pressure” will promote a procedure that most women end up not even needing—all “at great cost, great inconvenience, and a little bit of risk.” It’s also possible that the whole cold-storage approach to infertility could eventually be replaced by a better one: turning stem cells into egg cells, say, whenever a woman is ready to conceive.
But the biggest benefits of socking away young ovarian tissue may come at the other end of a woman’s reproductive life cycle. “One of the really big health challenges of the future is that we’re getting too old,” says Claus Yding Andersen, a professor at the Laboratory of Reproductive Biology at the University Hospital of Copenhagen. “The longer you’re in menopause, the greater your risk of osteoporosis and cardiovascular disease. The very best thing you can do to reduce those risks is to have your own menstrual cycles.” However they go about managing their fertility, women of the future who wait until their forties to start having children will probably want to put off the indignities of an aging body as long as possible. They will know they’ll need a spring in their step—not to mention sturdy hearts and flexible knees—if they’re going to keep up with those long-awaited kids.
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