Men Less Fertile After 40: Study

Men apparently have a biological fertility clock that ticks just as inexorably as that of women, reports Agence France Presse. New research reveals that a man's ability to impregnate a partner drops significantly once he reaches 40, regardless of his sperm count. It's the first clinical proof that a man's age has a direct effect on a couple's fertility.

"Even more surprising, the proportion of miscarriages went up as well," said a lead researcher. "We already believed that couples where the man was older took longer to conceive—but how DNA damage in older men translates into clinical practice has not been shown up to now." The French study examined outcomes of one of the most successful forms of artificial insemination. (More fertility stories.)