Babies delivered by cesarean section may be at 26 per cent increased risk of becoming overweight or obese as adults than those born by normal delivery, scientists including one of Indian-origin have warned.
The finding is based on combined data from 15 studies with over 38,000 participants.
The researchers, from Imperial College London, said there are good reasons why many women should have a C-section, but mothers should be aware that there might be long-term consequences for their children.
Around one in three to four births in UK are by cesarean section, around twice as many as in 1990. In some countries, the rate is much higher, with 60 per cent of mothers in China and almost half in Brazil having the procedure.
Some previous studies have suggested that the odds of other adverse long-term outcomes, such asthma and type 1 diabetes in childhood, are also higher in babies born by cesarean.
The new study, which includes data from 10 countries, found that the average BMI of adults born by cesarean section is around half a unit more than those born by vaginal delivery.
It is the largest to show a link between cesarean delivery and BMI in adulthood, researchers said.
The authors say they cannot be certain that cesarean delivery causes higher body weight, as the association may be explained by other factors that weren't recorded in the data they analysed.
"There are good reasons why C-section may be the best option for many mothers and their babies, and C-sections can on occasion be life-saving," Professor Neena Modi from the Department of Medicine at Imperial College London, the report's senior author, said.
"However, we need to understand the long-term outcomes in order to provide the best advice to women who are considering cesarean delivery," said Modi.
"This study shows that babies born by C-section are more likely to be overweight or obese later in life. We now need to determine whether this is the result of the C-section, or if other reasons explain the association," said Modi.
Dr Matthew Hyde, one of the researchers, said that there are plausible mechanisms by which cesarean delivery might influence later body weight. The types of healthy bacteria in the gut differ in babies born by cesarean and vaginal delivery, which can have broad effects on health.
"Also, the compression of the baby during vaginal birth appears to influence which genes are switched on, and this could have a long-term effect on metabolism," Hyde said.
The study was published in the journal PLOS ONE.
