Not so fast! Study suggests c-sections don’t cause child obesity after all

Cesareans: No problem?

Here’s a Brazilian study that claims cesarean section isn’t a risk factor for obesity, which contradicts other studies that suggest an association between the two. Interesting finding, but this will need to be confirmed in other countries. There may be something about Brazil–cultural factors like diet, for example–that may overshadow cesarean birth’s alleged obesity risk.

Bottom line: obesity is a complex topic, and there are obviously many factors involved. Cesareans still seem likely to be a contributor, but to what degree remains to be seen.


Filed under Cesareans, Obesity

9 responses to “Not so fast! Study suggests c-sections don’t cause child obesity after all

  1. MomTFH

    I would think that the cesarean rate in Brazil, which is up to 90% in private hospitals, might make it difficult to extrapolate these findings to other countries.

    PS Love the blog! Huge fan!


    • Good point, though a lot of countries are headed toward similar rates. I’ll post an interesting article on China’s skyrocketing cesarean rates soon. There are so many obesity risk factors that could be in play in a given culture that it’s hard to know – it’s going to take pretty extensive research to tease all this out. Still, as the article points out, there are a lot of other reasons to avoid an unnecessary cesarean, whether it’s a risk for obesity or not. (And I do think that it is.)
      Glad you’re enjoying the blog! Thanks for writing.


  2. Ytterbia

    But why would a cesarean delivery predispose a child to obesity in the first place? It makes absolutely no sense. The only thing I can think of is that this is just another way to demonize cesareans and make sure that we indulge our collective misogyny by forcing women to go through childbirth the old fashioned way.


    • Oops! I need to explain myself better sometimes…

      The possible link between cesarean birth and obesity has to do with the types of bacteria that end up living in the human bowel. A fetus has no bacteria in its bowel. During birth, babies born vaginally swallow bacteria from the birth canal, which go on to “seed” the baby’s bowel as nature intended.

      Those bacteria do a number of beneficial things for humans, including guiding the development of the newborn’s immune system. Over the eons our bodies have evolved to expect those “good” bacteria (we actually provide them with a fertilizer-like food to help them grow), so much so that we attack bacteria that shouldn’t be there in the first place.

      Which brings us to cesarean section. Babies born by cesarean, particularly if the mother wasn’t in labor at the time of surgery, swallow bacteria from the hospital environment during and after birth, rather than from the maternal birth canal. As a result, “wrong” bacteria can and do take up residence in the bowel, a situation that lasts for years, maybe even the baby’s whole life.

      As the baby grows, his or her immune system sets up a chronic, low-level inflammatory war with those “wrong” bacteria, which through a lot of complicated pathways can lead to abnormal absorption of fats from the bowel into the bloodstream, increased storage of fats in fat cells, and decreased efficiency of burning calories. That’s a ticket to obesity.

      The direct link between cesareans and higher obesity risks hasn’t been proven yet, but the evidence is stacking up that how you’re born does make a difference in this regard. (Cesarean birth also appears to increase a child’s risks of asthma, eczema, and other chronic diseases.) That’s why the Brazilian study is interesting, because it seems to contradict other research. Time–and a lot of baby-poop research–will tell!

      I hope that’s a helpful explanation. Please let me know if I can answer any other questions you have,
      Thanks for writing!


  3. One more thought – I’m not anti-cesarean section. My son was born via a medically necessary cesarean, and I know for a fact that both he and my wife would almost certainly have died in the old, pre-cesarean days. What I am “anti” is unnecessary cesareans – this is major surgery, with known (and no doubt some still unknown) risks for both mother and baby.

    What I am “pro” is vaginal birth for women for whom it’s a safe option (ie, the majority of pregnant women). I’m a pediatrician, and my professional focus is on children’s health, from birth through the end of high school, the ultimate goal being a healthy life. And when I stack up the pros and cons of childbirth, vaginal birth is going to be a healthier start in life for most kids.

    I’m also “pro” informed choice. In the end it’s up to a woman to choose the circumstances of her child’s birth, as much as that’s currently possible in our often polarized maternity care system. There’s a lot of passionate opinion out there, and often not enough facts. I’m trying to help bridge that divide.

    Again, thanks for taking the time to write,
    Mark Sloan


  4. Gillian Daley

    Mark, I find this understanding of how we “seed” the gut during birth to be fascinating and it seems like we are learning more each year about the role of bacteria in the health of our bodies. I wonder, knowing all of this, what your thoughts are on the prophylactic use of antibiotics in women who are GBS positive. I understand that there are potentially grave risks for an infected newborn but it seems that the old recommendations of treating based on risk factors (which is what the CDC recommends now only in cases of unknown status) seems to make much more sense in a time that we are increasingly understanding the risks of antibiotic resistance and the importance of well seeded, and well regulated, gut flora.


  5. Ytterbia

    Thanks for your thoughtful responses. I’ve heard the hygiene hypothesis discussed before but my understanding is that it is, at this point, not much more than a hypothesis. I recall reading one study that claimed a link between cesarean birth and asthma and finding the actual data rather unconvincing as the increased rates seemed to be related as much to gestational age as mode of birth. It’s a fascinating idea though, and I’m not dismissing it out of hand. I’d be very interested in reading more if you could point me to other studies that support this idea. Perhaps there is also some other way to introduce the beneficial bacteria?

    My concern is that I feel women are not being given truly informed choice and are being pressured into believing that cesareans are more dangerous than they are while the risks of natural childbirth are being downplayed. I’d hate to see more women being denied or discouraged from making an informed choice about the best way to deliver their babies because of unfounded fears or misinformation.


  6. Mark makes some good points on the topic.

    The hormones and bacteria a vaginal baby is exposed to by passing through the birth canal do play a significant role in the health of the baby.

    Babies deprived of these hormones and bacteria can have varying health consequences, unfortunately none of the data is conclusive. Many studies still have to be done,

    Very interesting topic though.

    Elizabeth 🙂


  7. 1) Department of Corrections:

    I got a bit ahead of myself (and the current research) in connecting the dots between cesarean birth and risks for later obesity, and thanks to Ytterbia and Elizabeth for catching my over-reach. To date there has been no proven link between the two, but the circumstantial evidence is mounting.

    2) Department of Wonk-Science:

    Here’s what IS currently known about gut bacteria and obesity:

    • The bacteria found in the bowel (known as the gut microbiota) of obese adults is characterized by an overabundance of Firmicutes species, a family of bacteria that triggers low-level inflammation in the bowel, which in turn plays a direct role in excessive fat absorption and storage. Therefore, inflammation caused by an immune system response to an abnormal gut microbiota directly promotes obesity in adults.
    • Babies born via cesarean section, particularly those whose mothers never went into labor, in general tend to have a firmicutes-heavy gut microbiota very similar to that seen in obese adults.
    • The gut microbiota acquired at birth and shortly thereafter tends to stay fairly stable from early infancy to adulthood.

    So, though no one has yet proven that a link exists between cesarean birth and risk for later obesity exists, it seems increasingly plausible that it does.

    But plausibility does not equal proof, and obesity is a very complicated subject. More research will undoubtedly come along on this topic soon. I’ll post it when it does.

    If any readers would like copies of some of the scientific reviews that cover this topic, please email me at and I’ll be happy to send them to you.


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