The optimum age for a woman to fall pregnant is 25 as fertility's at its peak and the risk of miscarriage and genetic conditions are at their lowest.

Women should consider starting a family not long after graduating from university as they risk a ticking fertility time bomb otherwise, a British expert says.

Focusing on a career, paying off student debts, finding a partner and getting on the housing ladder have all contributed to the age that women first conceive rising to almost 30.

Dr Gillian Lockwood, medical director of the Midland Fertility Clinic, said the optimum age for a woman to fall pregnant was 25 as fertility was at its peak and the risk of miscarriage and genetic conditions like Down's syndrome were at their lowest.

"Age 25 is exactly the time when today's young women have left university, are trying to get off on a good career, trying to pay back their student loans, trying to find someone who wants to have babies with them and trying to get on the housing ladder," Dr Lockwood said.

Dr Lockwood, who was speaking at an event discussing fertility at the Cheltenham Science Festival, says many women think IVF is the answer if they wish to have a child in later life but that also presents problems with a rapidly decreasing success rate
once a woman hits 40.

Research has shown that by the age of 40 there is a 12.1 per cent chance of IVF with a woman's own egg working and that decreases to 1.6 per cent by the age of 45.

"But the bleak reality is that the chance of IVF working with your own eggs once you are 40 is absolutely abysmal and in what other branch of medicine would we let, yet alone encourage, patients to pay for an elective operation with a less than 5 per cent chance of working?," Dr Lockwood said.

"The problem we have here is that women on the outside are shiny, young and youthful and on the inside their ovaries know exactly what it says on their birth certificate. As I always tell my patients - you cannot Botox your ovaries.

"The suggestion was made that since every proud father is looking forward to being an even prouder grandfather one day, perhaps the perfect graduation present for a 21-year-old daughter would be for her dad, instead of buying her a second hand car, actually did an egg freezing cycle for her because the current evidence is that if you have 15 nice mature young eggs you have got at least a 95 per cent chance of having at least one baby and that is better than any other branch of IVF.

"But I think there are quite worrying social consequences of allowing the generation gap to spread from 25 years to 40 years which egg freezing would encourage."

Dr Lockwood warned of the "sandwich generation" of a working mother looking after both her children and elderly parents.