Babies that are delivered by caeserean section are more likely to become overweight or obese as adults, according to researchers from Imperial College, London.
Compared with vaginal delivery, C-section increases the odds of being overweight or obese in adulthood by about a quarter, reports the team.
"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,” says lead author of the study Professor Neena Modi. “However, we need to understand the long-term outcomes in order to provide the best advice to women who are considering caesarean delivery.”
As reported in PLOS ONE, Modi and colleagues performed a systematic review and meta-analysis of anthropometric data available for 38,000 individuals who also reported their mode of birth delivery.
The study, which includes data from 10 countries, showed that overall, the average body mass index (BMI) among adults who were born by C-section was almost 0·5 kg/m2 greater than in those who were born by vaginal delivery.
Further analysis showed that those born by C-section were 26% more likely to be overweight (BMI >25 and <30) and 22% more likely to be obese, findings that were consistent across both genders.
"There are plausible mechanisms by which caesarean delivery might influence later body weight,” says co-author of the paper Dr Matthew Hyde.
“The types of healthy bacteria in the gut differ in babies born by caesarean 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," he explains.
However, the researchers conclude that there is now a need to determine whether the association they found between C-section and overweight and obesity in later life, is causal, or reflective of confounding influences.