Baby girls who are born by caesarean could be at higher risk of obesity and developing type 2 diabetes, new research has suggested.
Harvard scientists have found that women born by C-section faced an 11% higher risk of obesity and a 46% higher risk of type 2 diabetes, compared with those delivered by a natural birth.
This could be due to differences in the microbes babies are exposed to in their mother's birth canal when born naturally compared with those they face when delivered by caesarean.
The findings applied not only to high-risk caesarean births, but also to mums in low-risk categories for caesarean delivery based on maternal characteristics.
One in four babies are delivered by caesarean in the UK, according to a 2018 Lancet study.
In their new research, published by the JAMA Network Open, scientists explored possible links between a caesarean birth and the baby's risk of obesity and type 2 diabetes in adulthood.
Jorge Chavarro, study author from Harvard T.H Chan School of Public Health in Boston, said: "We found that being born by caesarean delivery was associated with an 11% higher risk of obesity and a 46% higher risk of type 2 diabetes.
"Whether these findings are applicable to men or to individuals born today, when caesarean delivery rates are substantially higher, is uncertain."
The study was based on more than 33,000 women aged between 24 and 44, of which around 3% were born by caesarean.
Almost 37% of women were obese while around 6% were diagnosed with type 2 diabetes during the study's follow up period.
Results revealed women born by caesarean were more likely to fall into this group than those delivered by natural birth.
The reasons behind the development of obesity and type 2 diabetes in adulthood among those born by caesarean remain unclear.
But growing evidence points to the hygiene theory and changes in the child's gut bacteria.
Gut bacteria can modulate chronic inflammation thus, changes in gut microbiota can be associated with fat and glucose metabolism.
Babies delivered through a natural birth are quickly colonised by microbes from their mother's birth canal and faeces.
While those born by caesarean are colonised by environmental microbes.
As a result, newborn babies delivered by caesarean harbour less diverse gut bacteria, particularly those which have shown to be protective against obesity.
But it is unknown whether it will last long-term.
Differences in DNA between children born by caesarean delivery and those by a natural birth have also been suggested as a biological explanation underlying longterm health outcomes of caesarean delivery but the evidence is scarce.
The study's findings were consistent across multiple strategies for accuracy reasons, suggesting that these links are consistent with a true biological association of birth by caesarean delivery.
But scientists said more evidence is needed to investigate whether babies born by caesarean are at higher risk of developing other adverse metabolic and cardiovascular conditions.