When I read about scientists from Harvard reporting last week in Nature Medicine that human ovaries contain stem cells that can grow eggs from scratch, I thought again about the chapter in Twentysomething about baby-making. (Seems like I have baby-making on the brain, if measured by this post and the one I wrote last week.) If the research is confirmed it will, first of all, counter the old dogma that females are born with all the eggs they’ll ever have, which has always explained why a woman’s eggs get progressively more damaged with age. But more than that, it will revolutionize our conception of assisted reproduction — and of how long young women can safely wait to start having babies.
What makes the research so interesting to me is how it will affect young women’s ideas about how long they can safely put off decisions about childbearing. Already, their sense that they can delay that decision almost indefinitely is a main driver of the delay among Millennials of achieving not only parenthood, but all the other traditional “milestones” of adulthood.
If eggs can be made fresh at any age, the way sperm can, will that further delay the onset of adulthood, which many people complain is already late enough?
It’s not clear, from my reading of the report, how often these ovarian stem cells actually make new eggs when left alone to do their own thing. It must not be too often, since a woman’s natural fertility suffers a sharp decline with age, and her eggs are clearly older and more prone to big problems with cell division and chromosomal damage.
Fertility inexorably declines with age: at age 30 it’s 20 percent lower than it was in the early twenties; at age 35 it’s 50 percent lower; at age 40, a distressing 95 percent lower than it was at its peak.
Here’s another way of looking at it: say a group of couples have been spending their time trying to get pregnant (the fun, old-fashioned way, with no syringes or Petri dishes). If the women in that group are 28 years old, 72 percent will get pregnant after trying for a year; if they’re 38, only 24 percent will. Much of this is no doubt attributed to old eggs, since a forty-something’s chance of pregnancy at an IVF clinic is significantly higher — almost the same as a twenty-something’s — if she is using donated (in other words, much younger) eggs. If these stem cells have been there all along and capable of maturing into eggs with fewer genetic abnormalities, why don’t they?
Obviously, many questions remain, and more research must be done to confirm these early findings. It’s much too soon for young women to make their reproductive decisions based on the remote possibility that when they’re finally ready to have babies — when the career is in high gear and the right partner is found and all the other pieces of a settled life have fallen into place — there will be fresh eggs aplenty.