BABIES are up to three times more likely to die soon after delivery if their mothers choose a Caesarean section rather than a normal birth, a big American study has shown.

The finding will come as a shock to the increasing number of women who opt to have a Caesarean, even if there is no medical need for it. Almost a quarter of British babies are born in this way.

It has been known for some time that baby deaths are higher after Caesareans than after normal vaginal births, but the reason was always thought to be that many operations were done as emergencies, when problems arose during labour.

The American study is the first to compare death rates after elective surgeries, when women chose the procedure in advance in consultation with their obsetricians. The cases chosen were those of women with no known medical reason for the procedure, or with no special complications during labour.

“Neonatal deaths are rare for low-risk women — of the order of one death per 1,000 live births,” said Marian MacDorman, of the Centres for Disease Control and Prevention in Atlanta, Georgia, who led the study. “But even after we adjusted for socioeconomic and medical risk factors, the difference persisted.

“These findings should be of concern for clinicians and policymakers who are observing the rapid growth in the number of primary Caesareans to mothers without a medical indication.”

The team studied more than 5.7 million live births and nearly 12,000 infant deaths in the United States from 1998 to 2001. They counted deaths among babies that occurred within 28 days of birth, called neonatal deaths.

They conclude in the journal Birth: Issues in Perinatal Care that the neonatal death rate for Caesarean birth among low-risk women was 1.77 deaths per 1,000 live births. The comparable rate among vaginal births was 0.62.

As in Britain, the rates of Caesarean operations have been increasing fast in the US, where they now account for 29 per cent of births. US Caesarean rates increased by 41 per cent between 1996 and 2004, while the rate among low-risk women nearly doubled.

Michael Molloy, a co-author and a professor of paediatrics at the University of Texas, said: “When obstetricians review this information, perhaps it will promote greater discussion within the obstetrical community about the pros and cons of offering Caesarean sections for convenience and promote more research into understanding why this increased risk persists.”

Belinda Phipps, chief executive of the National Childbirth Trust in Britain, said that earlier studies had given hints of such a problem. They had shown that respiratory distress was more common in babies born by Caesarean.

She said that the US study involved big numbers. “I think it does need to be taken pretty seriously. It seems to be something to do with the process of labour. The baby is squeezed very hard during labour, and it may be something like wringing out a cloth. Babies that don’t have this experience seem more likely to have problems with their lungs.”

The US team also suggests that the process of labour, as well as squeezing fluid out of the lungs, releases hormones that promote healthy lung function. Alternative explanations of the finding are that accidental injury to the babies during Caesareans, or the delayed establishment of breast-feeding, may contribute to the higher death rates.

• A study in France published last week indicates that Caesarean delivery more than triples a woman’s risk of dying in childbirth compared with a vaginal birth.

  Researchers led by Catherine Deneux-Tharaux, of the Tenon maternity hospital, Paris, looked at 65 maternal deaths recorded in the French National Perinatal Survey from 1996 to 2000.

  All of the deaths came after births of a single child and were not due to conditions existing before delivery. The women had also not had a hospital stay during pregnancy.

  The researchers found that the risk of death — from blood clots, infection or complications from anaesthesia — was 3.6 times higher for women who had Caesareans.

Times Recommends

• Donor organ allowed child’s own heart to heal
• Michael Jackson: Not the final chapter
• Brüno toned down for 15 rating