Cesareans, asthma, and eczema (Part 2)

Though mounting evidence associates cesarean birth with asthma and other immune system disorders (and I believe the link is real), it’s best not to jump to conclusions.

Association versus causation, Yankee Stadium

“Association” is often confused with “causation” in the popular press and online, and blurring the two has led to a world of confusion for people trying to figure out what the research is really saying. Just because ‘A’ and ‘B’ happen at the same time (ie, they are associated in time) doesn’t mean that ‘A’ caused ‘B’. (The firestorm caused by the association of vaccines with autism—they’re actually not at all related—is just one famous example of this.)

Here’s the difference between association and causation, baseball-style:

Say you and 40,000 other people attended a baseball game in Yankee Stadium the afternoon a peanut vendor was mugged, right in the middle of Section 201. Your presence at the game and the commission of the crime are associated (you were in the stadium at the time), but that doesn’t prove that you’re the one who caused the peanut guy’s bad day. Could be a coincidence and nothing more. So far there’s only a 1-in-40,001 chance you did it.

But if you were one of the 100 people seated in Section 201 when the mugging took place, the association is much stronger: we’re down to a 1-in-100 chance that you’re the baddie. Still no proof, but we’re getting closer.

Of course, if you’re the one the police nab with wads of peanut-scented dollar bills stuffed in his pockets and an angry-as-hell vendor clinging to his leg, we now reasonably have causation. Case closed. Off to the slammer with you.

So where is the cesarean-asthma association on the continuum of “just a coincidence” to “caught red-handed”? Hard to say at this point, but it’s certainly closer to sitting in Section 201 than it is to watching the commotion innocently from the opposite side of the stadium.

Here’s another thing to think about: maybe it’s not the cesarean per se that’s the culprit. Rather, it could be the things that directly lead to a cesarean, like poor nutrition, maternal obesity, or chronic diseases like asthma, diabetes, or heart disease, all of which increase the chances that a woman will need a cesarean, that make it more likely for a baby to develop asthma or other immune system disorders.

It could be hereditary. A woman who has asthma herself – which by itself puts her at higher risk of needing a cesarean – may simply pass on an “asthma gene” to her baby, making it look like the cesarean, and not genetics, caused her child’s asthma.

Or it could be something that happens during the cesarean. Intrapartum antibiotics—those given during the operation to prevent serious infection—can and do alter the immune-system-priming bacteria that reach a newborn’s bowel first, for example.

Regardless. Whether it’s the cesarean directly causing the problem, or something more obscure that is associated with cesarean birth, isn’t clear as yet…but something’s up.

Cesarean section has been a great boon to safer birth in the last century and a half – my own wife and son would likely not have survived without one – but the trend toward viewing cesareans as a routine alternative to vaginal birth is troubling for a number of reasons.

The cesarean-asthma link should be serious food for thought for any woman seeking an elective, medically unnecessary cesarean birth for her baby.

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4 Comments

Filed under Asthma, Cesareans

4 responses to “Cesareans, asthma, and eczema (Part 2)

  1. As an asthma sufferer and the recipient of an emergency c-section, this is fascinating! I am also tremendously happy to see your blog, I recommend your book to all of my friends, pregnant or just interested in pregnancy/babies/how the body works. I can’t wait to read more.

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  2. Hi Amber – thanks for your comment, and for your kind words about Birth Day. I’ll be revisiting this issue in the future, since there is new information coming out all the time. A reduced cesarean rate would be a good, healthy idea for a number of reasons, and this is just one of them.
    Take care – Mark Sloan

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  3. Thank you for replying, Mark! We’re planning our second and final child (planning a pregnancy and birth is definitely not as easy as it sounds), and I constantly go over the repeat c versus vbac debate, I know it’s supposed to be an easier recovery if I have a vbac, but I worry I’ll end up needing a c-sec after all anyway. The internal debate continues.

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  4. Hooray for including the shout-out to the possibility of genetic inheritance. I have asthma (and eczema, and a long laundry-list of environmental and food allergies), my daughter was born via C-section (neither of us would have survived without it), and she (so far, she’s 5) hasn’t shown signs of asthma at all (tho she does show minimal signs of other allergies). And aside from the asthma issue, my allergic profile is quite similar to my mother’s, and hers is quite similar to her mother’s. When I was pregnant and “told” that eating peanuts wold cause my unborn child to develop an allergy, I always sighed, annoyed. My Mom didn’t eat fish or shellfish when she was pregnant, thus her eating habits couldn’t have directly caused my allergy. The etiology of immune system functioning is clearly multi-causal and much more complex than we currently know. I always appreciate folks who are willing to acknowledge that we don’t live in a world of “main-effects,” rather the causal story always reflects a multi-factorial interaction.

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