More than 75,000 British babies a year are born to fathers aged 40 and over –that's more than one in 10 of all births – and more than 6,000 of these babies have dads aged over 50.

Such dads have very famous counterparts, of course – Rod Stewart was 60 when his youngest son, Alistair, was born, Michael Douglas was 58 when his wife Catherine Zeta Jones gave birth to their daughter Carys and Charlie Chaplin was 73 when he had son Christopher.

While not quite reaching daddy Chaplin's impressive years, the average age of men who father a child in the UK is certainly creeping up, and now stands at 32. And while a new study has found that men around this age enjoy being a father the most, it also concluded that becoming a father has the biggest effect on dads in their late 40s. Of dads aged between 46 and 50 questioned in a study by Colief Infant Drops, 46 per cent said fatherhood had changed their perspective on life.

Adrienne Burgess, research manager at think-tank The Fatherhood Institute, says this will be because older fathers have lived more of their lives and are ready for changes.

"In the 1970s when people had babies younger, a lot of the dads weren't anywhere near ready, financially and in other ways," she says.

"Now that it's happening more when they're older, they're in a better place."

Burgess points out that while the age of fathers is increasing, plenty are second time around dads because of family breakdown.

"Many of them are in a position to feel more confident financially, and they're also embracing the idea of being able to be closer to their children, which hadn't been acceptable before.

"They've been released and allowed to do it, in a way."

However, the Colief survey found older dads (aged 46-55) said fatherhood had left them out of pocket, with 43 per cent saying the expense was the worst thing about being a dad. In contrast, 37 per cent of younger dads (aged 22-25) thought lack of sleep was the worst aspect.

Burgess admits: "Older dads who are becoming fathers for the first time in, say, their late 40s, are more likely to be financially worried."

And, while older fathers may rejoice at becoming a dad, there are possible health implications for their babies.

A recent Danish study found that children whose fathers were over 45 when they were born were almost twice as likely to die before reaching adulthood as those fathered by men aged between 25 and 30.

The findings may be linked to the declining quality of sperm as men age.

Previous studies have also found that children of older fathers are more likely to have Down's syndrome, or suffer congenital defects such as heart and spine problems, as well as develop rare childhood cancers and conditions including autism, schizophrenia and epilepsy.

It's an alarming catalogue of potential problems, but Burgess suggests that such negative outcomes are "very strongly" linked to lifestyle factors, and stresses.

"An older dad who hasn't had a life of bad health is much more likely to have a child that's okay.

"The health messages need to get out there to dads – and men who want to be dads, whatever their age."

Dr Allan Pacey, senior lecturer in andrology – the study of male reproduction – at the University of Sheffield, says that while a bad lifestyle will certainly "make things worse", age alone can still have its own effects.

He says: "It's not been studied in a controlled way, but it's certainly not the case that leading a healthy lifestyle will protect fathers from the effects of ageing."

He says that any man above the age of 40 would be considered an older father – 40 is the age at which men will no longer be accepted as sperm donors, for example.

"The list of problems which can result gets a lot longer after a man gets to the age of 40," he warns.

"We've known for a long time that the older a father is, the more likely his offspring are to have health problems.

"They're not as common as those related to older mothers can be – you're still more likely to have Down's because your mum was older than because your dad was older – but the effect is still detectable statistically."

Pacey also warns that men above the age of 40 are thought to be about half as fertile as men aged under 25, explaining that although older men still have the same number of sperm, "clearly there's something happening at molecular level."

He adds: "The risks of having a baby with a problem when you're older are small, but they're detectable. What I would say is if you're delaying having children for no good reason, perhaps just because it never seems to be the right time, you should really think again."