Women should consider starting a family not long after graduating from university as they risk a ticking fertility time bomb otherwise, according to an expert.
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.
"It may not be true that women should be having babies at the time of the GCSEs but they shouldn't leave it much later than graduation," Dr Lockwood said.
"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, who was speaking at an event discussing fertility at the Cheltenham Science Festival, said that many women think that 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% chance of IVF with a woman's own egg working and that decreases to 1.6% 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% 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% 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.
"You have mum in the middle, who is still working full-time, she has got truculent teenagers or possibly even truculent toddlers at home and she is also trying to look after her demented elderly parents because she doesn't want to put them in a home," she said.
"One of the most poignant aspects of the spreading generations is that we might lose this wonderful relationship between grandparents and grandchildren.
"If you have got an 80-year gap between their grandparents and their grandchildren it is very difficult for them to have that rich and rewarding relationship that we all grew up with.
"We could end up with this zimmer frame-cum-pram-cum-shopping trolley for the elderly woman who decided that aged 55 was a really good time to have that baby she always wanted and unfortunately she has got some nice eggs that she had frozen at 25. Is this really where we want to go?"