More babies born via caesarean section grow up to be heavy kids and teens
than those delivered vaginally, according to a new study of more than 10 000 UK
Eleven-year-olds delivered by C-section, for example, were 83% more
likely to be overweight or obese than their vaginally-born peers once other
related factors - such as their mother's weight and how long they were breastfed
- were taken into account.
The findings are in line with a recent review of nine earlier studies that
also found a link between C-sections and childhood obesity. With C-sections,
"there may be long-term consequences to children that we don't know about," said
Dr Jan Blustein, who led the new study at the New York University School of
Implications of C-sections
The rate of C-sections in the US has been rising, leading to concerns about
possible complications for mothers and babies. According to the Centers for
Disease Control and Prevention, C-sections accounted for almost 1 in 3 births in
2010 - up from 1 in 5 in 1996. For women, the procedure increases the chance of
bowel or bladder injuries as well as future pregnancy complications.
Blustein said the size of the obesity risk for kids is "not great," and
shouldn't come into play for women who need a C-section for medical reasons.
But, "a woman who's considering C-section electively should probably know
about those risks," she said. The researchers analysed data from babies born in
Avon, UK in 1991 and 1992 who were followed through age 15. Just over 9% of the
infants were delivered via C-section.
On average, kids delivered by C-section were born slightly smaller - by less
than two ounces - than those who went through vaginal birth.
Starting at six weeks of age, however, C-section babies were consistently
heavier than vaginally-born infants at almost all check-ins. That link was
especially strong among children born to overweight mothers, Blustein and her
colleagues report in the International Journal of Obesity.
What the study
Across the whole study group of children, rates of overweight and obesity
ranged from 31% at age three to 17% at ages seven and 15. Blustein said studies
haven't been able to prove whether C-section, itself, is a reason some babies
tend to gain more weight.
If it is, she speculates, it might have something to do with C-section babies
missing out on important exposures to friendly bacteria during the trip through
the birth canal. "Generally, the early colonisation and establishment of the
intestine with bacteria seems very important. Yet, much more work is needed
before we can explain the mechanisms of the early bacterial colonisation,"
Teresa Ajslev, from the Institute of Preventive Medicine in Frederiksberg,
For example, there may be a specific type of bacteria that's protective, said
Ajslev, a researcher and PhD student who has studied pregnancy-related impacts
on childhood weight but wasn't involved in the new report.
Or bacteria imbalances could more generally disrupt intestinal function in a
way that promotes obesity. Either way, if the exact cause could be identified,
it might be possible to give C-section babies doses of the missing gut bugs to
But it's also possible bacteria have nothing to do with the obesity link to
C-section births. "The other possibilities are (that) these are children that
would have been heavier anyway," Blustein said.
"Being heavy as a woman is a risk factor for C-section, so that's the problem
with trying to figure out whether this is real or if it's simply a matter of
selection," since overweight parents are more likely to have overweight
Her study was able to take a mother's weight into account, and did find the
link between C-section births and child obesity was "weak" among kids born to
But there could be other unmeasured factors that help explain the overall
link between delivery method and a child's weight.
"This certainly is not the last word," Blustein said.