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Women who choose a Caesarean delivery, sometimes described as "too posh to push", are increasing the risk to themselves and their baby.
Surprise results from an international study of 97,000 deliveries show that a routine Caesarean puts a woman at twice the risk of illness or death compared to a vaginal birth.
And babies born by Caesarean had a 70 per cent higher risk of dying before discharge from hospital if they were lying normally head first in the womb than if delivered vaginally.
A Caesarean delivery was, however, found to be safer for babies lying in the less common and riskier breech position - feet first.
The findings are from eight randomly selected countries in Latin America, where Caesarean rates are higher than in the UK, at an average of 33 per cent of all births.
Well-heeled Latin American women are more anxious about the potential effects of a vaginal birth on their sex lives and in some private hospitals the Caesarean rate is up to 60 per cent.
In Britain, the Caesarean rate has doubled in the past 20 years to 22 per cent, driven in part by the demand of some women for what is perceived as a convenient and pain-free method of delivery.
Obstetricians too have seen it as safer - and as a way of reducing risks of litigation.
The latest study, published online in the British Medical Journal, suggests the safety of Caesareans may have been overstated.
Jose Villar, former director of maternal health at the World Health Organisation and now a senior research fellow at the University of Oxford, who led the study, said there was no benefit from the very liberal use of Caesareans, either for mothers or babies, and they could even do harm.
Caesareans led to longer hospital stays for mothers and babies, increased the risk of readmission and increased the risk to subsequent pregnancies.
The only exception was that babies in the breech position did better and women had fewer severe vaginal complications.
Dr Villar said the findings should be applicable to Europe and the UK because of the large number of deliveries surveyed, the comparability of outcomes to those in Europe and because the overall Caesarean rate was not dissimilar.
"The message is that a woman thinking of having a Caesarean because it is safer should think again," he said.
"It is a question of balancing the risks and benefits. She should sit down with her care provider and consider the options. We think this is the most comprehensive study that has been done."
In a commentary on the findings, Alison Shorten, of the School of Midwifery at the University of Wollongong, New South Wales, Australia, said an important reason why women chose Caesareans was because of worries about damage to the pelvic floor from a vaginal birth, which could lead to sex and bladder problems.
"Women need to weigh up the possible but uncertain benefit of preventing urinary problems against the increased chance of problems related to surgery in themselves or their baby," she said.
Pat O'Brien, consultant obstetrician at University College Hospital, London, and a spokesman for the Royal College of Obstetricians and Gynaecologists, said: "We have always known from the mother's point of view a planned Caesarean was slightly riskier.... Recent research from the US has suggested the risks of the two approaches were getting closer and closer. This latest study pushes that back a bit."
- INDEPENDENT