Half of women who do not want pain relief will need it / Alamy

Childbirth hurts – rather like taking your bottom lip and pulling it over your head, in the unforgettable image conjured by the American comedian Bill Cosby – but too many women today are being wrongly led to believe that a pain-free and drug-free labour is possible, a dream that is shattered by reality.

A review of 32 studies of women's experiences of childbirth has revealed that hope too often triumphs over reality. The experiences of most women differ markedly from their expectations, which can lead to disappointment when labour does not go according to plan.

"Childbirth is one of the most painful events that a woman is likely to experience... A woman's lack of knowledge about the risks and benefits of the various methods of pain relief can heighten anxiety," say the researchers from Newcastle University's Department of Public Health.

Joanne Lally, who led the investigation, said antenatal education programmes needed to adopt a more honest approach. "Women should go into labour with hopes of what they want it to be but they should also be realistic about what it is likely to be," she said. "If they want a natural labour that is fantastic and they should be supported in that. But if the pain gets too much and the decisions are taken out of their control that is when it goes wrong and they can end up feeling disappointed. Women need to be fully equipped beforehand with the information to make decisions."

The review published in the online journal BMC Medicine found that, in one study, more than half the women who said they would not use pain relief ended up needing it. In a Swedish study, women were able to give the pain a positive meaning, as when one mother said: "I think it's a happy pain, though its hell."

Researchers concluded that positive attitudes to pain reflected satisfaction with the way they had coped with it, rather than the pain itself. In most studies the pain was worse than expected – in only one was it better than expected.

Mary Newburn, head of policy at the National Childbirth Trust, said: "Pain is tied up with fear and anxiety. If women are provided with good support they may be able to cope with the pain and have a good experience and emerge triumphant."