The biological clock can't tick backward

June 28, 2000|By Zev Rosenwaks

NEW YORK - At 48, Wendy Wasserstein becomes a first-time mother-to-be and chronicles her triumph in the New Yorker. The pregnancies of Annette Bening and Jane Seymour make headlines. Other stories tell of women having babies using their own eggs, their husbands' sperm and surrogates' uteruses. The nonstop media parade of midlife women producing offspring is stunning.

These stories are about the fortunate ones: They beat the odds.

There is no doubt that the remarkable and ever-expanding repertoire of reproductive technologies can help women have babies at almost any age. Yet, as an infertility specialist, I often see women - and men - who have been lulled into a mistaken belief that there is a medical technique that will allow women to have their genetic children whenever they choose.

There is nothing yet in medicine's portfolio that can guarantee women in their fourth, fifth and sixth decades that they will reproduce. Still, in our eagerness to outwit time, the media have made a best seller out of the freshly minted fiction of "rewinding the biological clock."

We can't and we haven't. There are certain ineluctable truths. Each woman is born with a finite number of eggs, and the genetic quality and viability of those eggs will diminish as she ages. The natural reduction of ova and follicles will continue until the ovaries are depleted, around the age of 50. For most women, fertility begins its decline in the early 30s. It plunges at 35. It takes another precipitous dip at 39 and drops steeply and steadily thereafter.

Yet we are bombarded by reports of celebrity pregnancies and by inspirational stories. We hear of women having four, five, up to eight babies, or of postmenopausal women carrying children to term.

So, of course, it comes as a brutal shock when women of a certain age, no matter how youthful looking, find biology has betrayed their expectations.

Certainly medicine has made astounding advances. Technology has markedly improved the fecundity rates for midlife women. A woman at 40 who wants to conceive with her own eggs but does not use "assisted reproduction" has a much smaller chance for success as a 40-year-old who does.

Yet even as science pushes back the age of reproduction, the efficacy of these sophisticated technologies is still capped by nature's attrition of ova and follicles and implantation rates. An in vitro fertilization patient who is 30 is three times more likely to become pregnant than her 40-year-old peer.

Women who contemplate postponing childbearing should know that they may not be able to conceive with their own eggs. Past a certain point, their only option to have the singular experience of pregnancy and childbirth is ovum donation - that is, using someone else's genetic material.

Yes, donor eggs are something of a miracle, a wonderful alternative to building a family that is more commonly used than people think. But using another woman's egg means that the birth mother will not be passing on her family's genetic history - eye color, height, perhaps a musical ear or a mathematical bent.

Down the road, researchers may find ways to reverse the biological attrition rate, discovering a technique for creating a new gamete, either egg or sperm, from an individual's DNA. Perhaps the cryogenic preservation of eggs, still fairly primitive, will improve enough so that a woman can bank her young ova for future use. If science does breach biology's barriers, we have no guarantee these procedures will be safe enough for everyone.

Then there's the big question: If we can turn back time, does that mean we should?

Until we find the answers, practical and philosophical, we have no choice but to accept nature's timetable. My colleagues and I do all we can to help women who want to conceive.

But we must put the fable of rewinding the biological clock back on the shelf with the other fairy tales and give women the tools to write more realistic happy endings.

Zev Rosenwaks is director of the Center for Reproductive Medicine and Infertility of New York-Presbyterian Hospital-Weill Cornell Campus. Pamela Madsen of the American Infertility Association assisted with the writing of this article, which first appeared in the New York Times.

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