Tag Archives: Asthma

Cesareans and chronic childhood disease: Time for a public discussion

From the Ishinhō, Japanese medical text, 1860

From the Ishinhō, Japanese medical text, 1860

In an analysis published in the most recent edition of The BMJ, Drs. Jan Blustein and Jianming Liu examine the evidence that cesarean delivery is associated with an increased risk of chronic childhood diseases like asthma, type 1 diabetes, and obesity. Their conclusion: the bulk of the evidence suggests that the association is real.

The time has come, Blustein and Liu write, for maternity care providers to include the risk of chronic childhood disease in their discussions with women considering a “non-essential” cesarean, such as when the choice is between a VBAC or repeat cesarean, or in the case of a woman choosing a medically unneccessary cesarean in lieu of vaginal birth—the so-called “maternal request” cesarean.

This topic has intrigued me for some time now. As part of my recently completed MPH program at the University of Minnesota, I wrote a paper titled, “Do Cesarean Sections Increase the Risk of Child Asthma? A Systematic Literature Review.”

In writing the paper I read and analyzed every research study on the subject since 2001. Roughly two-thirds of those studies detected a small-to-moderate association between cesarean birth and childhood asthma. (In fact, 90% of the studies detected an association between the two, but not all were statistically significant.) Most of the studies that didn’t find the association were seriously flawed—too few subjects, for example, or ignoring possible confounders, like prematurity or a history of maternal asthma. Three meta-analyses (two in 2008, one in 2014) all reached similar conclusions: cesarean section is associated with about a 20% increase in the risk of child asthma.

My paper was limited to asthma, but as described in the BMJ analysis there’s evidence that cesareans increase the risk of other chronic childhood illnesses, too–type 1 diabetes and obesity. A 2015 study by Sevelsted et. al. analyzed a cohort of two million Danish children and found small-to-moderately increased risks of juvenile rheumatoid arthitis, connective tissue disorders, inflammatory bowel diseases, immune deficiencies, and even leukemia.

Given that body of evidence, you’d think that organizations like ACOG (the American Congress of Obstetricians and Gynecologists) and the U.K.’s National Institute for Health and Care Excellence would be pushing their members to share this information with their pregnant patients. But they’re not. According to Blustein and Liu,

“…knowledge about chronic disease risks could affect decision making in non-essential caesarean. The American College of Obstetrics and Gynecology and the UK’s National Institute for Health and Care Excellence recently issued consensus statements on caesarean delivery at maternal request. Based on evidence about maternal and perinatal outcomes, both groups concluded that a pregnant woman requesting caesarean should have that choice, if she still desires it after discussion of the risks and benefits of the procedure. Importantly, neither group acknowledged the long term risk of chronic disease. [Emphasis mine.]

Critics can (and do) point to the uneven quality and designs of the studies that support such links—it’s association versus causation all over again—but that’s not entirely fair. To prove beyond doubt that cesarean birth increases the risk of child asthma, you’d have to do trials where women are randomly assigned to cesarean or vaginal birth…which, as you can imagine, is a practical and ethical non-starter. That leaves us with observational studies, which can only point out that two things seem to be related, not that they definitely are.

Ah, but there has been a randomized study of the long-term effects of cesareans versus vaginal birth in term, breech deliveries, and at least one research team has made the case that randomized trials of mode of delivery aren’t really unethical. More on those topics soon.

Finally, just to re-re-reiterate: I’m not anti-cesarean. My wife and son are alive and well today thanks to a medically necessary cesarean. But the cesarean rate today is 6 times higher than it was when I was a junior in high school (1970, if you must know…). As Blustein and Liu point out in their analysis:

“We live in a world where caesarean rates cannot be explained by compelling medical indications.”

Perhaps increased awareness of the potentially negative impact of cesareans on child health will help reverse that decades-long trend.

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Cesareans and asthma: More evidence

No way to spend a childhood...

Yet another study links cesarean birth with asthma. This one involved 37,000 participants in the Norwegian Mother and Child Cohort Study, and compared cesarean- and vaginally-born children for evidence of asthma at age 3. Those born by cesarean section had an increased risk of asthma.

The authors speculate that the altered gut microbiota found in cesarean babies–the collection of bacteria that live in the bowel–may be the reason for the association. (See my posts here and here for an explanation of how and why an altered gut microbiota may be at the root of a number of later chronic illnesses.)

The study’s authors described the increased risk as “slight,” which contrasts with the “moderate” risk found by other researchers. This apparently lower risk may be due in part to the how the study was performed.

First, the researchers lumped all cesareans–both scheduled cesareans and those that followed a long labor, in which a baby may be exposed to the normal bacteria of the birth canal–rather than comparing scheduled cesareans to vaginal births. The latter comparison would give a clearer picture of childhood asthma risks from cesarean birth.

Second, the study only follows the children to 3 years of age. Many cases of asthma occur later in childhood, and a longer follow-up of these children (which is no doubt in the works) would give a clearer picture of the risks.

Studies like this one add more weight to the argument for reducing the number of cesareans currently being performed, particularly those done without any medical need. Women should be informed of the potential long-term health risks and benefits for their children when choosing how and where they want to have their babies.

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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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