- The Washington Times - Tuesday, September 6, 2016

Researchers at Harvard this week announced a possible link between cesarean section births and obesity that raises new questions for expectant parents to ask about potential long-term health risks.

Newborns delivered by cesarean section are 15 percent more likely to be obese than babies passed through the birth canal, according to a team of researchers at the Harvard T.H. Chan School of Public Health.

“Cesarean deliveries are without a doubt a necessary and lifesaving procedure in many cases,” the study’s lead author Jorge Chavarro, associate professor of nutrition and epidemiology at Harvard Chan School, said in a statement. “But cesareans also have some known risks to the mother and the newborn. Our findings show that risk of obesity in the offspring could [be] another factor to consider.”

The group’s findings were published Tuesday in JAMA Pediatrics and corroborates previous studies that have drawn similar conclusions based on far less data.

“Our group’s original motivation to conduct this study was to show that the association between cesarean birth and higher risk of childhood obesity that others had reported was solely due to the fact that many of the reasons that cesareans are performed — such as maternal obesity, excessive weight gain during pregnancy, large babies and gestational diabetes — are also risk factors for childhood obesity,” co-author Aubrey Gaskins told ResearchGate.

“We expected that after controlling for these other risk factors in our analysis, the association between cesarean birth and childhood obesity would completely disappear. That was not the case,” she said.

The researchers took into consideration more than a dozen variables before examining the long-term health data of more than 22,000 individuals whose medical history is on file and accessible through the school’s Growing Up Today Study (GUTS) program.

While only 13 percent of the people included in the sample were obese in adolescence or later, the researchers determined that the odds of developing obesity were higher for the 22 percent of participants who had been delivered by C-section compared to those who weren’t.

Babies who were delivered by C-section without it being medically necessary were 30 percent more likely to be obese between the ages of 9 and 28 than those delivered vaginally, according to their study.

Compared with siblings delivered through the birth canal, C-section babies are 64 percent more likely to be obese than their naturally birthed brothers or sisters, the researchers added.

“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,” Mr. Chavarro said. “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.”

While the group’s stopped short of offering an explanation for its conclusion, researchers pointed toward the possibility of babies getting essential microorganisms from the birth canal prior to delivery.

“The most compelling mechanism supporting this association is differences in gut microbiota. At birth, our bodies are colonized by bacteria,” Ms. Gaskins told ResearchGate. “Children born by vaginal delivery are primarily exposed to their mothers’ vaginal and gut microbes, whereas children born by cesarean are primarily exposed to bacteria on their mothers’ skin and whatever bacteria happen to be in the air in the operating room.

“This initial difference in mode of delivery leads to changes in the type of bacteria living in children’s guts,” she said. “Moreover, the pattern of gut bacteria that children born by C-section tend to have has been previously linked to greater risk of obesity later in life.”

Doctors in the United States perform about 1.3 million C-sections each year, making up roughly one-third of all deliveries in the country.

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