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No link between caesareans, weight: study

chubby baby hand and fingers

When you factor in all of these other factors, the relationship between obesity and Cesarean sections disappears, says the lead researcher (Source: Benjamin Howell/iStockphoto)


Past research from Brazil had found a link between excessive weight and caesareans, leading some scientists to suggest that not being exposed to bacteria from the birth canal could make children fatter. But the latest findings, published in the American Journal of Clinical Nutrition , suggest this isn't the case.

The research is of particular interest in Brazil, because in 2009 more than half of the babies there were born by caesareans. In Australia and the United States, the number has been on the rise for years and is now around 30 per cent.

"We thought from the beginning that probably what happened with the previous study is that they didn't adjust for all of the confounders," says Fernando Barros of the Catholic University of Pelotas , who worked on the study, referring to factors such as the mother's height and weight.


Researchers contacted the children at different ages until the oldest had turned 23 years. Those born by caesarean were more likely to be heavy, with obesity rates between nine and 16 per cent, compared to rates of seven to 10 per cent of children born vaginally.

However, that difference vanished once the researchers accounted for factors such as family income, birth weight, schooling and the mother's weight, height, age and smoking habits.

"When you factor in all of these other factors, the relationship between obesity and Cesarean sections disappears," says Barros.

The earlier Brazilian study left out many of those factors, including maternal height and weight, Barros's team wrote in its report.

"The really simple explanation would be that more obese women require more Cesarean sections than lean women... and it's really not the caesarean itself," says David Ludwig, director of the Optimal Weight for Life Clinic at Children's Hospital, Boston, who was not involved in the study.

Birth canal benefits

He says that things such as a pregnant woman's diet and smoking habits, and whether or not she has diabetes, might influence a developing foetus.

Some believe that caesarean babies are different because they are not exposed to bacteria in the birth canal like babies born vaginally. The theory is part of a hypothesis which suggests that a person's immune system develops differently when they're not exposed to beneficial bacteria early in life.


Tags: infant-health, obesity, pregnancy-and-childbirth, babies-newborns