Experts advice men to have kids before 40 in order to raise their chances of having healthy children

It's not just women who have a biological clock – men are being warned to become fathers by 40 or face a greater risk of having children with serious illnesses. Fertility specialists said men were not as immune to reproductive ageing as they might have thought. They advised them to complete their family before they hit 40 to minimize the chance of having a child with Down's syndrome, autism or mental illness. The warning follows a review of studies into the effect of a father's age and lifestyle on his child's health. One found that children of men aged at least 40 were almost six times more likely to be autistic than those of fathers under 30. It is thought that as a man gets older, the sperm he makes is more likely to be damaged.
Worryingly, some of the effects may pass through the generations, with a man's grandchildren being affected as well as his children. The review also warns that the amount of alcohol a man drinks may affect children he conceives. For instance, a baby can be diagnosed with foetal alcohol spectrum disorder, which causes attention problems, hyperactivity and poor co-ordination, even if the mother never touched booze. Study author Joanna Kitlinska said: 'Up to 75 per cent of children with foetal alcohol spectrum disorder have fathers who are alcoholics, suggesting that pre-conceptional paternal alcohol consumption negatively affects their offspring.'
Research also links parental alcohol use with smaller brains and lower intelligence, while smoking may also be damaging. Dr Kitlinska's round-up also highlights studies linking male obesity with diabetes and brain tumours in the next generation and paternal stress with behavioural problems.
Allan Pacey, a fertility expert at Sheffield University, said: 'The best advice to men, in order to maximise their chances of fathering a healthy baby, is to try and have a family before they are much older than 40. Above this age, we know that attempts at pregnancy are generally less successful.  Even with a younger partner, rates of miscarriage increase in frequency and there are measurable increases in the incidence of some disorders, such as schizophrenia, autism and birth defects in their children.'
But other experts claim almost all children born to older fathers are healthy – and 'no one needs a licence to reproduce'.
Professor Alastair Sutcliffe, a child health expert at University College London, said: 'It may well be that the downsides of older fatherhood can be offset by the upsides, such as being calmer and economically generally better off.'
However, Professor Adam Balen, chairman of the British Fertility Society, said: 'Young people need to be aware of the factors that affect fertility.
'Hence the need to support young couples to develop their careers and establish relationships so they can start families when they are more fertile and less likely to run into difficulties.'