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Good eggs

There is no place for ageism in reproductive medicine.

Earlier this year, Harvard researchers turned dogma on its head by showing that, in mice, eggs are produced well into adult life (Nature 428, 145–150; 2004). This suggests that the menopause occurs not when eggs produced by the embryo eventually run out, as previously thought, but when cell death outpaces egg production in the adult ovary. If this is true for humans, the implications for treating infertility and health problems related to the menopause are profound. But it would be unfortunate if the suitability of older mothers also became a prominent part of discussions.

It is appropriate to scrutinize the societal impacts of any research, but a double standard may exist with regard to fertility. Men who father children into their golden years are more likely to receive back slaps than pressure to stop. In contrast, many fertility clinics deny services to women over 50, and even as young as 45. The American Society for Reproductive Medicine's ethics committee discourages oocyte donation to postmenopausal women, citing a variety of concerns relating to the medical condition of mother and baby, as well as the psychological effect on the baby of having an older mother.

In truth, the likelihood that any individual will be a good parent depends on a variety of factors, only one of which is age. And while it is true that children of older parents have a higher risk of birth defects, this can be lessened by screening high-risk embryos for genetic defects before implantation. As for the medical risks, a 2002 study showed that pregnancy for women in their fifties from in vitro fertilization (IVF) is just as safe as for younger women who had IVF from donor eggs, and found no reason to exclude women over 50 from pregnancy on the basis of age alone (J. Am. Med. Assoc. 288, 2320–2323; 2002).

Delaying the menopause is usually viewed in the context of fertility research, the subject of this week's Outlook (see page 37). Current research may help to prevent the debilitating conditions that arise when ovaries come to the end of their natural working lives. Even now, women spend nearly half their lives in menopause, an experience that can range from mild discomfort to debilitation. Osteoporosis is associated with loss of ovarian function, and there is evidence that cardiovascular disease, mood disorders, neurological problems and diminished sex drive are also connected. Genetic mouse models in which the menopause is delayed may eventually help disentangle which health risks are a direct consequence of menopause, and which are brought about by ageing (see Nature Genetics 21, 200–203; 1999).

Whether the menopause is seen as a medical condition requiring treatment or a phase of life to be tolerated, it is clear that, as human lifespan is extended, the ability to delay the menopause will be attractive to many women. Hormone-replacement therapy is no alternative to functioning ovaries, so it is to be hoped that a better understanding of ovarian regeneration will lead to improved treatments.

Research into women's reproductive health is important for its potential benefits to quality of life and overall health. It should not be sidetracked by detractors who make the patronizing and outdated argument that older women shouldn't have babies that they will be too old to care for.

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Good eggs. Nature 432, 1 (2004). https://doi.org/10.1038/432001a

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