Researchers have found that babies born via caesarean delivery have a 15 percent increase in the chance of becoming obese when compared with children born vaginally. With a third of all babies in the US now born though C-sections, this could have a highly significant impact on the future health of these children. Not only that, but the likelihood of developing obesity was even greater within families, with babies born via caesarean 64 percent more likely to be obese than their siblings who were born vaginally.
“I think that our findings – particularly those that show a dramatic difference in obesity risk between those born via cesarean and their siblings born through vaginal delivery – provide very compelling evidence that the association between cesarean birth and childhood obesity is real,” explains Jorge Chavarro, co-author of the study published in JAMA Pediatrics. “That’s because, in the case of siblings, many of the factors that could potentially be playing a role in obesity risk, including genetics, would be largely the same for each sibling – except for the type of delivery.”
This is not the first study to show that by bypassing the vagina, babies are at a higher risk of developing chronic conditions. Previous research has found that caesarean babies are more likely to go on to develop not only obesity, but also type 1 diabetes and asthma. This study was unable to rule out that other factors were in play, for example, the mother’s age at the time of birth, yet this latest research has been able to control for such factors.
The team of scientists from Harvard University looked at a total of 22,068 children born to 15,271 women. By using such a large cohort, they were able to rule out potentially conflicting factors, such as age and blood pressure at time of birth (which make caesarean delivery more likely), and by looking at the siblings too they were even able to rule out more specific environmental fluctuations that may impact the chance of a child developing obesity. The average difference in weight between siblings was maintained into early adulthood, putting an extra 0.3 points onto the participants' BMI score.
What is causing this effect is not entirely understood, but it is thought highly likely that it's linked to the passing on of the mothers gut microbiome, or ecosystem of bacteria, to the child as it travels through the vaginal canal. It is becoming increasingly clear that the microbiome has an incredible role to play in the health of people, and disruptions in it has already been shown to affect obesity in adults. It is thought that by bypassing the transfer of the microbiome during the caesarean, the babies may miss out on acquiring critical gut bacteria.