Children born via cesarean section are slightly more likely than babies delivered vaginally to become heavy or obese, according to a new meta-analysis.
The results don't prove that c-sections cause kids to put on weight, but Dr Jianmeng Liu, one of the authors of the study and a professor at Peking University Health Science Center in China, said the link between the delivery and obesity is important to keep in mind.
"The potential health burden of obesity and other diseases associated with c-section births should not be neglected, even if its impact is modest," particularly given how often births happen that way, Dr Liu said.
Previous research has tied c-sections to a variety of untoward health outcomes in children, including asthma, allergies and diabetes.
How the study was done
Dr Liu said the relationship between the type of delivery and obesity among kids hasn't been as clear. The research team collected the results from nine studies that included more than 200 000 people.
People were 33% more likely to be overweight or obese if they were born by c-section, they reported in the International Journal of Obesity. The risk for childhood obesity in particular was somewhat higher - about a 40% increase over kids born vaginally.
Dr Liu said the increase in risk was modest, but that it persists into adulthood. When the researchers looked just at the studies on adults, they found that those who were born by c-section were 50% more likely to be obese than those who were born vaginally.
It's not clear why c-sections are tied to a better chance of being heavy. One possibility relates to the bacteria babies are exposed to when they are delivered vaginally, which might affect the way they process and store food, said Dr Liu.
C-sections linked with lower concentration
Additionally, Dr Liu added, researchers have suggested that c-sections are linked with a lower concentration in the umbilical cord of a hormone important in regulating weight and with a reduced rate of breastfeeding, "both of which are reported to be associated with an increased risk of later obesity."
Babies who are larger than normal are also more likely to be born via cesarean, but most of the studies Liu's team analysed took into account birth weight.
In the US now, one in four babies is born via c-section. Dr Liu said there's been concern that some of these are unnecessary, and given the potential negative impacts on children the unneeded ones should be curbed. "In clinical practice, (the) potential adverse impact of c-section should be considered by medical staff, and non-medically indicated elective c-section should be somewhat avoided, where possible," Dr Liu said.
(Reuters Health, Kerry Grens, December 2012)
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