Does cesarean birth put a baby at increased risk for obesity in the future? Seems a little far-fetched at first glance, but Dr. Susanna Huh and her Harvard colleagues just published a study that makes the link a bit more “near-fetched.” (The study itself is available here.)
Huh’s team found that children born by cesarean section were twice as likely to be obese at 3 years of age than were those born vaginally. This relationship held up even when factors like the mother’s weight, ethnicity, age and how many babies she’d already had were taken into account. Interestingly, it didn’t make a difference whether the cesarean was performed before or after labor started.
The study wasn’t designed to look at the reasons for the increased risk in obesity, but the Harvard team suggested several possibilities:
The first is the alteration of the gut microbiota–the sum total of all the bacteria found in the human bowel–caused by a cesarean birth. (More detail on that here and here.) This alteration can lead to low-level inflammation in the bowel which is associated with obesity.
The second possibility is that cesarean birth is just a stand-in for something else that’s happening at the same time. In this case, Huh and colleagues wonder about all the antibiotics given to women who are having cesareans. Antibiotics are known to alter the gut microbiota, but research results are mixed as to whether this is a lasting effect.
Finally, it’s possible (though unlikely) that all of this has nothing to do with the gut microbiota. There are hormones and other factors related to inflammation that surge in a mother’s bloodstream (and her baby’s) during labor, and these, obviously, are missing if a mother undergoes a cesarean before she starts labor. The lack of maternal stress response during labor could adversely impact the development of the newborn immune system, leading to the inflammation associated with obesity.
My best guess: it’s a big moosh of all of the above, plus other factors no one has even dreamed of yet. In the meantime, the issue of increased obesity risk is one more thing physicians and pregnant women should consider before deciding on how a baby is to be born.
It’s a complicated matter, this business of hatching healthy humans…