The male biological clock can reduce chances of fatherhood as early as a man’s late thirties or early forties, research has suggested.

Miscarriage rates start to climb when the prospective father is older than 35, and rise sharply after 40. Pregnancy rates also fall when men are in their forties, a French study of more than 12,000 couples has found.

The findings, from a team led by Stéphanie Belloc, of the Eylau Centre for Assisted Reproduction in Paris, add to evidence that shows male fertility starts to dip at an earlier age than once thought. Several studies have shown that DNA damage in sperm increases markedly after the age of 35.

The miscarriage rate was 16.7 per cent per pregnancy when men were aged 30 to 34, 19.5 per cent between 35 and 39, 32.5 per cent for the over 40s and 32.4 per cent for over 45s.

Dr Belloc said that the findings had implications for couples trying for a baby when either partner was over 35. As both maternal and paternal age can reduce the chances of pregnancy, it may be worth considering IVF at an early stage if they fail to conceive naturally. “I think it’s important to consider not only the woman, but both members of the couple in natural conception but also in assisted reproduction,” Dr Belloc said. “We believe that the use of IVF should be suggested to infertile patients where either party is over 35 years of age.”

Jacques de Mouzon, of the French National Institute for Medical Research, another member of the study team, said: “People say men are fertile into old age, 90 even. That may be true sometimes, but the product is different. There is a decrease for men in fertility and an increase in the spontaneous abortion rate. It is necessary for men to try to have children before the ages of 40 to 45.”

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