A new study has revealed that IVF success rates decline significantly after a man turns 51.

Up until now, couples have been told to focus on the woman’s fertility window, in the belief that men can easily father children well into middle age and beyond.

Now, the scientists behind the study are calling for a fertility experts to advise men to listen to their biological clock and not to put off fatherhood.

The research was carried out at London’s Centre for Reproductive and Genetic Health, and involved the analysis of 5,000 IVF cycles.

The results showed clinical pregnancy rates declined with increasing paternal age.

Specifically, success rates in men under 35 were at around 50 per cent, but this fell to around 30 per cent in men aged over 51.

According to the Centre for Reproductive and Genetic Health, previous studies have revealed a decline in natural male fertility with age, but until now it wasn’t known whether paternal age affected IVF outcomes.

At the moment, some clinics set an upper age limit on female IVF patients, yet no such limits exist for males.

Dr Morris said: “There may well be a public perception that male fertility is independent of age. Stories of celebrity men fathering children into their 60s may give a skewed perspective on the potential risks of delaying fatherhood.

“Indeed, in natural conception and pregnancy it is only recently that evidence of risks associated with later fatherhood has become available.

“These more recent studies contrast with decades of evidence of the impact that maternal age has on fertility outcomes.

“In the context of this emerging evidence for the deleterious effect of increasing paternal age, our data certainly support the importance of educating men about their fertility and the risks of delaying fatherhood.”