Women often get ridiculed for being a "cougar" and going with another man, although doctors say this is smart for older women who want to get pregnant. 

A recent study says it's actually the man's aging sperm that is more likely to be the cause of an older couple having problems getting pregnant. 

Michael Dahan, of McGill University in Montreal, and his colleague Noof Al-Asmari, studied 631 women between the ages of 40-46 using IVF, a process where an egg is ferilized by a sperm outside of the body in a test tube. The partners of the women being studied ranged from ages 25-73. 

"Younger women's eggs can fix any defects of genetic material of the sperm. But once a woman hits 40, that's no longer true. It suggests once the woman is reaching 40 and the man is in his early 40's as well, the male is having a biological clock," Dahan tells Daily Mail. 

Most of the couples in the study who had difficulties giving birth had one consistant factor - the man was most likely above 43-years-old. 

This was the first study to ever prove that men could also have a biological clock. Previously it was believed that men could always father a child, despite their age, because they are always producing new sperm. Women, on the other hand, are working with the same eggs that they started out with at birth throughout their entire lifespan. 

The new findings in this study were presented at the American Society for Reproductive Medicine's annual conference in Honolulu.