Women seeking IVF are often advised to quit smoking
Almost half of fertility experts say access to IVF should be conditional - and smokers or the obese could be denied treatment, a survey shows.
The poll of international experts, most of whom work in the UK, found just 29% thought IVF should be offered to all.
Obesity and smoking have been linked to fertility problems, so doctors say it is fair to ask patients to change their habits before they are given care.
Patient groups said lifestyle advice should be based on medical evidence.
The poll asked for doctors to agree or disagree with the statement "access to IVF should be conditional on criteria based on lifestyle choices - eg denying access to smokers".
Professor Peter Braude, a leading fertility specialist based at Kings College London, said: "The biggest issue is weight, where there is clear evidence that it can decrease the chance of getting pregnant, if someone is significantly over or under-weight.
"The evidence on smoking isn't conclusive, but there is research showing it can affect ovulation."
He added lifestyle had to be considered: "We don't send patients away because they smoke. But we do suggest patients stop smoking, cut down on alcohol and are a healthy weight."
Clare Brown, chief executive of patient group Infertility Network UK, said: "We always encourage those who contact us to try and adopt a healthy lifestyle when trying to conceive."
But she said: "Such criteria should not be used as an out and out barrier to treatment."
New procedures 'rushed in'
The survey was carried out to mark the 30th anniversary of the birth of the first IVF baby, Louise Brown, who was born at Oldham and District Hospital in Greater Manchester on July 25, 1978.
It also found 85% of fertility experts want more clinical trials to test the efficacy of new techniques.
And more than half agreed that new procedures are being offered to patients far too quickly and before trials have adequately assessed their efficacy.
It follows the introduction of a technique called preimplantation genetic screening (PGS), designed to check embryos for abnormalities so the best ones could be implanted.
But a report last year found it actually reduced the chances of a woman becoming pregnant after fertility treatment.
Although most IVF specialists work in the private sector, over 70% of those polled thought fertility care should be funded by a country's health service.
Leaving it too late
Around two-thirds thought demand for IVF would increase over the next 30 years, partly due to a predicted increase in male infertility - because of factors such as exposure to hormones in the water supply.
However, experts say much of the increase will be due to more people waiting longer to try for a baby.
Dr Allan Pacey, secretary of the British Fertility Society, said: "It's expected that people will be magicians and can reverse the ageing process.
"I think many people in the profession find it frustrating.
"IVF should be a last resort, and starting to try five years earlier might make things better."