More than a third of women say they have had fertility problems, according to a survey which suggests that many are leaving it too late before they think about trying to conceive. The study, commissioned by Red magazine, said that many women did not appear to realise that peak fertility would be in their 20s and fertility would sharply decline from their mid-30s.

"Women were saying they thought the ideal age to have a baby was 27, but most women don't think about having a baby until just before their 30th birthday. Women thought if it didn't work out, they could always have IVF. They didn't realise only one in four cycles resulted in a pregnancy and they didn't realise the cost," said a spokeswoman for Red.

The survey of 3,200 women found that not all those who said they had fertility problems needed treatment. They included women who said it had taken them more than a year to conceive. Of the 3,200, 7.3% had paid for IVF and 4.4% were having IVF treatment at the time they responded to the questions asked by the online survey company Demographix.

The cost of a cycle of IVF treatment is about £3,000. The government has agreed to one free cycle on the NHS for each couple who need it, but it is not available in all areas of the country.

Among the women surveyed, IVF was not always successful. Less than half of those who had treatment (47%) went on to become mothers. "Women don't seem to realise that if they really want to become a mother one day, maybe they should start to think about it at an earlier age," said the spokeswoman.