Sperm donors up to the age of 45 are just as likely to conceive children as those in their 20s, a large study has shown.
The findings dispel the myth that a woman's chances of IVF success are lowered if she has to rely on sperm from an older man.
By encouraging more men to come forward as donors, they could help alleviate the sperm shortage faced by fertility clinics.
But researchers warned that older men in the general population should not assume they are as fertile as their younger peers.
This is because all men who get through the stringent donor screening process, almost by definition, have high quality sperm.
Dr Navdeep Ghuman, from Newcastle Fertility Centre, who took part in the study of more than 230,000 sperm donation treatments, said: "What's reassuring is that there's no decline observed with increasing age of the men.
"The scary idea in the media and women's minds that older sperm means less chance of conceiving wasn't seen.
"We wanted to answer the question, does the age of a sperm donor matter? The short answer is no, it doesn't."
Using data stored by the fertility regulator, the Human Fertilisation and Embryology Authority, researchers analysed the success of sperm donations from men aged 20 and under to 45.
They found that live birth rate fell with the increasing age of women, dropping from 29 per cent for those aged 18 to 34 to just 14 per cent for the over-37 age group.
But within each of these groups, the age of the sperm donor had no impact. In fact, a slightly - non significant - greater proportion of sperm donors aged 41 to 45 fathered children than did those in their 20s.