Doctors should try to persuade pregnant women not to have a Caesarean if they do not need one, experts say.
Women can be anxious about giving birth
But guidelines from the National Institute for Clinical Excellence say doctors ultimately have to allow a woman to choose how she gives birth.
They say women must be told about the risks and benefits of different ways of having a baby.
Around 1.5% of all births in England and Wales are Caesareans carried out for non-medical reasons.
Although these women - often dubbed "too posh to push" - make up a very small proportion of births, experts say they still want to reduce the number of women who have operations they do not need.
However, doctors stress that emergency Caesareans and the majority of planned Caesareans are necessary, and carried out to ensure the health of both the baby and the mother.
A national audit showed that in 2001, 21.5% of babies in England and Wales were born by Caesarean.
The World Health Organization says the rate should be between 10 and 15%.
The proportion of babies born by Caesarean vary from 18 to 25%, depending on the region, but individual hospital's rates vary from 6 to 66%, mainly because some see more complicated pregnancies than others.
Experts say that the number of Caesareans carried out for medical reasons could be reduced if maternity units changed the way they work.
They suggest a range of tests and other measures which could prevent the need for a Caesarean.
For example, a common reason for the operation is if the baby is in the breech position, which would make a natural labour more dangerous.
But the guidelines say some babies can be manipulated externally so they are in the correct position to be born naturally.
Other simple ways to reduce the chance of a woman having a Caesarean include having a woman, whether a midwife, a relative or a friend, present during labour to reassure and support the mother-to-be.
Men can become distressed at seeing their partner in pain, or try to take control of the situation.
Giving a woman isotonic energy drinks, like those drunk by marathon runners, can also help a woman cope with labour better, reducing the chances that she will want to have a Caesarean.
The new guidelines are aimed at ensuring women have the same kind of advice and care wherever they live.
The guidelines say women should be told that, although they would avoid labour pains, and complications such as bladder problems or prolapse of the womb, women who have Caesareans are more likely to have a blood clot or need further surgery
They also increase the chance of babies having breathing problems.
Jane Thomas, Director of the National Collaborating Centre, told BBC News Online: "These guidelines are about women making informed choices.
"They have to be told about the risks and benefits about the decision they're making.
"Women who want to have a Caesarean are often anxious about giving birth. They should be talked to about their fears."
But she stressed doctors would be looking to offer women more information. "We're not trying to talk them out of it."
Professor David James, Professor of Foetomaternal Medicine and Director of Medical Education, Queen's Medical Centre, Nottingham, said his unit had reduced the rate of Caesareans from 29% to around 21% by extending the non-surgical tests and support it offered.
Louise Silverton, of the Royal College of Midwives welcomed the aims set out in the guidelines, but added: "They cannot be fully implemented because there is a shortage of midwives."
Mary Newburn, Head of Policy Research, National Childbirth Trust, said many women were anxious because they had not seen relatives or friends giving birth and were frightened - and so believed Caesareans were the "easy option".
She added: "It's important that women should feel able to make decisions that are right for them."