Women who have had a caesarean section are at greater risk of stillbirth in a later pregnancy, a report suggests.
Social trends have resulted in more women requesting caesareans
University of Oxford experts studied 81,784 births where the mother had previously had a caesarean and found the chances of stillbirth were higher.
The data came from women in West Berkshire and Oxfordshire who gave birth between 1968 and 1989.
The risk for women who had had the process was 4.6 per 1,000 compared with 3.5 per 1,000 for those who had not.
The research, published in the British Journal of Obstetrics and Gynaecology (BJOG), was carried out by experts at the department of public health at the University of Oxford.
The researchers believe problems with "formation of the placenta, a genetic predisposition and environmental factors" could be to blame.
Dr Ron Gray, from the National Perinatal Epidemiology Unit, who led the study, said: "This is now the fourth study of this kind to have shown an increased risk.
"We would suggest that further research is required to understand why this is happening.
"In the meantime, pregnant women and clinicians need to be aware of the potential increased risk, but should also be aware that the risk to any particular pregnancy is very small."
The experts also said the study was retrospective and caesarean sections have increased from 7.1% to 25% since the late 1980s.
'Too posh to push'
They said if the study was therefore replicated today, the number of stillbirths following caesarean could be higher than the 4% found.
Professor Phil Steer, editor-in-chief of BJOG, warned women should be aware of the risks if they were having the operation for "lifestyle reasons".
"Consultant obstetricians will recommend caesarean sections as a last resort and the procedure is generally safe for mother and baby," he said.
"However, social trends over the last few years have resulted in more women requesting caesarean sections."
His comments come after critics have reportedly said the rising caesarean rate is partly due to some women being "too posh to push".