Younger men produce more fertile sperm than older men, right? Wrong. A new study out of the U.K. has flipped that theory on its head. And its researchers have even gone so far as to suggest that sperm donations from older men may be more likely to result in pregnancy than donations from their younger peers.

The new study, which was presented at the Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Germany, found that women using donor sperm from men aged 40 and over were more likely to get pregnant than those using sperm donations from younger men. Researchers looked at pregnancy and treatment data from 40,000 women who used donor sperm between 1991 and 2012 and found that there was no difference in sperm quality between sperm donors in their 20s and those in their 40s. 

If anything, women were more likely to get pregnant from sperm that came from older donors. The study's authors hypothesize that the reason for this is that these older men are more likely to have families of their own and have a proven history of fertility — which may be a basis for selection.

Current guidelines set the maximum age that men can be sperm donors at 40, but this research has prompted some to suggested that the age be raised to 45. Still, it's important to note that sperm from older men has also been associated with birth defects and other health disorders for their children. So while sperm from older men may be more likely to result in pregnancy, this research does not give any indication about what affect that sperm may have on the future health of the child.

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