Size really does matter when it comes to fertility as a new study suggests men who are infertile are also less well endowed.

Having a shorter appendage was more common in men who were struggling to conceive than in those with other genital health problems. The research, to be presented at the American Society for Reproductive Medicine conference in Colorado this week, is the first ever to link penile length with fertility.

It found that on average, men who were infertile were around one centimetre shorter than their fertile counterparts. Those without reproductive issues had an average length of 13.4 cm while those in the infertile group were 12.5cm.

Dr Austen Slade from the University of Utah, Salt Lake City who led the study, said healthy men should not begin to fret over their size and their chance of becoming a father. Instead, he said underlying conditions that caused infertility, such as hormonal issues or problems in the testes, may also lead to a shorter penile length.

“This is the first study to identify an association between shorter penile length and male infertility,” he said. “It's possibly a manifestation of congenital or genetic factors that predispose one to infertility. For now, men with shorter penises don't need to worry about their fertility.”