May 24, 2012 -- Childhood obesity and cesarean delivery rates have skyrocketed over the last few decades, and intriguing new research suggests the two might be related.
Birth by C-section was associated with a two-fold increase in obesity at age 3 in the study by investigators from Harvard Medical School and Harvard School of Public Health.
Double the Obesity Risk
In the newly published study, investigators followed 1,255 children from birth until after their third birthdays, during which time 16% of children delivered by C-section became obese, compared to 7.5% of children delivered vaginally.
The association held even after the researchers considered the impact of known risk factors for childhood obesity, including the mother's weight, how long she breastfed, and the child's birth weight.
If future research confirms that C-section delivery is directly linked to early obesity, the implications are clear, says Harvard Medical School assistant professor of pediatrics Susanna Y. Huh, MD, MPH, who led the study.
"One in three children in the U.S. is now delivered by cesarean section," she tells WebMD. "If surgical delivery is a risk factor for child obesity, this would be yet another reason to avoid cesarean sections that are not medically necessary."
As for how C-sections may be linked to obesity, the researchers mentioned some possible explanations, but at this point they are all just theories. The link will require more research to determine if there is an actual cause and effect.
New York ob-gyn Mitchell Maiman, MD, believes a large percentage of C-section deliveries performed in the United States fall into the category of "not medically necessary."
Maiman is chairman of the department of obstetrics and gynecology at Staten Island University Hospital, near New York City, where close to 1 in 5 babies is delivered by C-section.
Nationwide, the rate is around 1 in 3 babies, but Maiman says he knows of individual hospitals with surgical delivery rates as high as 40%.
"Nobody really believes that a 40% C-section rate is ideal, but it is happening anyway," he says.
Huh says the latest findings add to the mounting evidence that so called "C-section on demand" may have lasting health implications for babies.
"We believe that mothers who choose to have cesarean sections without a medical reason to do so should be made aware that their child might have a higher risk for obesity," she says.
'Moms-to-Be Not to Blame'
While he agrees that far too many unnecessary surgical deliveries are being performed in the U.S., Maiman says mothers-to-be are not to blame.
"Everybody talks about how women are demanding C-sections, but this is almost a non-issue in this country," he says. "The fact is, physicians are the ones demanding the C-sections for their own convenience and because of the medical-legal climate. If something goes wrong and they get sued, the question is always, 'Why didn't you do a C-section?'"
Maiman says a major strength of the new study is that an association between C-section delivery and childhood obesity was seen even after the researchers controlled for known obesity risk factors.
"These findings certainly need to be replicated, but this may be one more indication that C-sections may not be the best thing for babies," he says.