Scientists have found a possible reason why women lose their fertility in middle age, in a discovery that could pave the way for treatments to extend women's childbearing years.

In a series of experiments on eggs from women getting fertility treatments, researchers learned that the function of several DNA repair genes weaken with age. This decline is accelerated in women near the end of their childbearing years, according to the results published in the journal Science Translational Medicine.

The experiments hint at why the female biological clock runs out as women reach their early 40s. The ability to repair DNA inside egg cells may become impaired, leading to accumulating damage to the eggs that causes them to die off more rapidly, said Kutluk Oktay, senior author on the study and a professor at New York Medical College in Valhalla.

In the study, the researchers took eggs from 24 women ages 24 to 41. In laboratory experiments, they found that the DNA repair genes were much less active in eggs from older women than younger women, indicating a decreasing ability to repair DNA damage to the eggs that occurs over time.

Women are born with about 1 million egg cells in their ovaries, Oktay said. Yet, when women reach their late 30s the eggs start to degrade at a much faster rate, for reasons that have long been mysterious.

-- Bloomberg News

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