No, C-sections Are Not “Best With a Little Labor”

Children born by C-sections have about 20% higher odds of obesity, asthma, allergies, and Type 1 Diabetes, according several large research reviews.

But are children born by scheduled C-sections especially at risk for health problems, as a recent New York Times piece claims?

“the data showed more health problems among babies born by planned C-section than among those delivered by emergency C-section or vaginal birth, even though the planned surgery is done under more controlled conditions. The finding suggests that the arduous experience of labor — that exhausting, sweaty, utterly unpredictable yet often strangely exhilarating process — may give children a healthy start, even when it’s interrupted by a surgical birth.”

A reader, confused by this New York Times piece, wrote to ask for my take. “Are planned C-sections really less safe?” she asked. “The actual study… didn’t seem to support what the NYTimes article claimed.”

And after reviewing the research myself, I have to agree.

The study in question, led by Dr. Mairead Black of the University of Aberdeen, and one of the largest and best-designed studies on long-term health following delivery by C-section, actually did not find more health problems among children born by planned C-sections than those born by emergency C-sections.

(The sole exception was an unexpected–and probably artifactual–increase in Type 1 Diabetes; more on this in a moment).

How Does This Study Fit in With What We Already Know?

Although C-sections have been consistently linked with poorer long-term health in children, scientists are still not sure why.

One possibility is babies miss out on the “sweaty and exhausting” experience of labor. The physical trauma of birth kickstarts the baby’s internal stress response, pumping cortisol through their veins, and giving their organs, including the lungs, the final push to full maturity.

Another possibility, favored by many scientists, is that C-sections alter the baby’s gut microbiome. C-section  babies miss out on the messy, bacteria-laden, splash into every bodily fluid passage through the birth canal–the route by which nature normally seeds a baby’s gut microbiome.

“If a baby is born naturally, it comes into contact with bacteria from the mother, which might help with immune system development,” lead researcher Dr. Mairead Black told The New York Times.

Compared to babies born by C-section, babies born vaginally have a more diverse and healthy gut microbiome–believed to be critical for their development of a healthy, balanced immune system (one good at attacking pathogens, but not overly jumpy and prone to self-attack).

Or perhaps the issue is not C-section birth per se, but the hodgepodge of pregnancy and birth complications that often result in C-sections, such as stalled labor, intrauterine growth restriction, and preterm birth.

To study one piece of this puzzle, the importance of labor-induced fetal stress, Black and colleagues at the University of Aberdeen in the UK compared babies born by planned versus emergency C-sections. Babies born by planned C-sections experience no labor, while babies born by emergency C-section often experience some, even though it is cut short.

Black and colleagues followed over 300,000 full-term singleton babies born to first-time mothers in Scotland between the years 1993 and 2007. Roughly 4% were born by planned C-sections, and 17% by emergency C-sections.

Compared to children born by emergency C-sections, babies born by emergency C-sections were at no higher risk of virtually every health outcome Black and colleagues assessed–asthma, inflammatory bowel disease, obesity at age 5, cancer, or all-cause mortality. In fact, these children born by planned C-section had a wee bit lower risk of dying during their first year of life.

The one exception: Children born by planned C-section appeared to have 50% higher risk of developing Type 1 Diabetes. (A 50% higher risk sounds scary, but because Type 1 Diabetes is rare, this amounts to only 2 additional diagnoses for every 1000 children.)

As the researchers acknowledge, the apparent increase in Type 1 Diabetes was probably not caused by birth by planned C-section, but by some artifact of their study’s design, a third factor not adequately accounted for in their research.

Why did they think this effect was not real? Because children born by planned C-section were not at higher risk of Type 1 Diabetes compared to children born vaginally, a pattern of results inconsistent with prior research, and one which makes little sense. If anything, the researchers expected the opposite, planned C-sections would lower the risk of Type 1 Diabetes. Earlier research has found severe fetal distress stress during labor–something obviously more common during emergency C-sections than during planned ones–raises the risk of Type 1 Diabetes.

My guess? The researchers were unable to completely account for maternal Type 1 Diabetes. Having a mother with Type 1 boosts a child’s chances of Type 1 Diabetes by about 10-fold. (Black and colleagues did try to control statistically for maternal Type 1 Diabetes, but were missing this information for some of the mothers.) To avoid complications during labor, many women with Type 1 Diabetes deliver by planned C-section.

C-sections Versus Vaginal Births

How did the children born by C-section fare compare to those born vaginally?

Overall, children born by C-section, planned or emergency, were more likely to be hospitalized for asthma and had higher mortality rates during the first year of life as well as throughout childhood.

Contrary to earlier research, though, children born by C-section were no more likely to develop inflammatory bowel disease, Type 1 Diabetes, obesity, or cancer.

The Bottom Line

The NYT headline is misleading: Planned C-sections do not lead to worse health outcomes than emergency ones.

The one exception: children born via planned C-sections had a 50% higher risk of Type 1 Diabetes, but only compared with unplanned C-sections. No difference was seen when comparing children born by planned C-section with those born vaginally, a pattern of results which, as the researchers themselves acknowledge, does not make any sense. In fact, this pattern runs counter to prior research, which suggests severe fetal distress during labor ups the odds of Type 1 Diabetes, and a recent meta-analysis which found that C-sections of all types up the odds of Type 1 Diabetes by about 20%.

Why is birth by C-section associated with poorer health? We still do not know. Given the impossibility of randomized controlled trials for childbirth, we may never know.

But this study does have one take-away: missing out on labor-driven stress response is probably not the critical issue. If it were, we would see significantly worse health outcomes among children of planned C-sections than emergency C-sections.

As for the risks of C-sections overall, that’s too big of a topic for me to tackle here. But I will say this: C-section-driven health risks are minor. They are almost certainly swamped out by who we are–the genetic blessings and curses we bestow on our offspring–and what we do as parents.

(Not reassured? You can always swab your C-section-born baby’s skin and mouth with your vaginal secretions, as widely-respected gut microbiome researcher Rob Knight did after his wife’s emergency C-section. I certainly would.)


Questioning Breastfeeding’s Benefits Does Not Make Me Anti-Breastfeeding

Earlier this week, I wrote about the alleged benefits of breastfeeding being vastly overstated.

My goal in writing that post was not to nurse some long-standing grudge against breastfeeding advocates. Nor was it an attempt to justify my own parenting choices: I breastfed both my children for well over a year.

(And yes, as some readers have inquired, I know just how wonderful breastfeeding can be. How breastfeeding your baby can be calming and joyful, even magical. But whether I found breastfeeding magical or a chore–or, in actuality, both–has nothing to do with whether it lowers the risk of asthma, or heart disease, or anything else.)

In response to my post, someone shared this comment on Facebook:

“Anyone who thinks this [my post] a solid piece of work needs to read my latest book, Milk Matters: infant feeding and immune disorder. No one has to prove that breastfeeding (the evolutionary and physiological norm that provides free stem cell transplants) makes a positive difference. Those who assume, claim or promote artificial feeding as safe or adequate need to prove that deviating from such basic physiological norms is safe, that there are no short or long term harms from doing so. …”

I am sharing this comment not because I find it particularly compelling, but because I think it nicely illustrates the problem with arguments made by many breastfeeding advocates: They start with the assumption that breast is best. And then, inevitably, they fail to scrutinize the evidence, no matter how flimsy, that supports that assumption.

And the evidence is flimsy indeed. Most of the alleged benefits of breastfeeding are found only in observational studies, which are widely acknowledged as biased. On average, breastfeeding mothers have a higher levels of education, higher incomes, and live in safer neighborhoods than formula-feeding mothers, granting their children an early leg up in life. Separating the effects of breastfeeding from these other advantages is next to impossible.

How do we know that these observational studies are biased? Primarily because we do not find the same benefits in better-designed studies–sibling comparison studies and the PROBIT randomized controlled trial. The only clear-cut benefit seen in these studies is a lower risk of severe vomiting and diarrhea during infancy. (For a detailed summary, see my earlier post).

To be fair, breastfeeding advocates are right, in a way. Breastmilk does contains numerous hormonal, antimicrobial, immunological, and nutritional factors not found in formula. This is why breastmilk helps protect against vomiting and diarrhea during infancy.

Before the advent of clean water, sanitation, and modern medicine, breastfeeding was frequently life-saving. In countries where access to these resources remains limited, it still is. There’s no bigger possible benefit than survival.

But these beneficial properties do not imply that breastmilk has any long-term benefits for the panoply of modern ailments: allergies, asthma, obesity, type 2 diabetes, and cardiovascular disease. We cannot claim such long-term benefits without sound empirical evidence. And that is entirely lacking.

If the American Academy of Pediatrics, and others were to say, “We recommend breastfeeding because it reduces the risk of severe diarrhea and vomiting during infancy, and because breastmilk contains unique immune, hormonal, and nutritional factors not found in formula, the long-term benefits of which are unknown,” I would have no problem with their claims.

But instead, they have chosen to present poor quality evidence as fact. Playing fast and loose with the evidence in this way undermines their credibility. Worse, it violates the trust that women have placed in them.

Breastfeeding Benefits: The Real, the Imagined, and the Exaggerated

Breastfeeding lowers your child’s risk of obesity, asthma, and allergies. Or does it? The best available research implies these claims are vastly overstated.

Breast is best is the mantra of most major medical organizations. Women have it drummed into them well before giving birth. Many women make themselves miserable pumping round the clock trying desperately to get their babies this “liquid gold”. Yet, for all the hype, solid evidence for benefits of breastfeeding, at least in the developed world, is lacking.

Here’s the thing about those oft-stated benefits: They only show up observational studies. 

Why does that matter? Because observational studies of breastfeeding all suffer from the same huge flaw: Breastfed infants tend to differ from formula-fed infants not just in how they are fed in infancy, but in nearly every other possible way–in their mother’s education level, in their mother’s IQ, poverty, neighborhood safety, exposure to environmental toxins, race, and type and quality of childcare. In scientific terms, breastfeeding is confounded, out the wazoo.

We cannot tell which benefits found in an observational study derive from breastfeeding rather than from the myriad other advantages linked with breastfeeding.

(The “good” observational studies attempt to control statistically for the other relative advantages of breastfed infants. Unfortunately, controlling for confounds only works well when (1) all the important potential confounds are known, and (2) when there is sizeable overlap between the compared groups. Neither is true when it comes to breastfeeding.)

In an ideal world, we would settle this question by conducting several large randomized controlled trials (RCTs), in which new mothers would be randomly assigned to breastfeed. RCTs are the gold standard in medicine for determining whether a true cause and effect relationship exists. In practice, though, such trials are neither feasible nor ethical.

Fortunately, we have the next best thing: a handful of studies that have cleverly circumvented the problem of confounding. These fall into two categories:

  • sibling studies, which compare siblings from the same families who were breastfed for different lengths of time, or who were not both breastfed.
  • a large RCT of a highly successful breastfeeding intervention (PROBIT Trial).

(Is the PROBIT Trial an exception to the no-RCT rule? No. Women in the PROBIT trial were not randomly assigned to breastfed or not; they were randomly assigned to receive a breastfeeding intervention or not.)

After my friend and I spoke about his irritation with the medical organizations like the American Academy of Pediatrics (AAP) and NHS overstating the benefits of breastfeeding, I was dissatisfied with my vague sense that he was right. I wanted to know exactly which benefits had been oversold and exactly which were supported not just by observational studies but by better-designed studies.

The short answer: Nearly all the alleged long-term benefits are likely the result of confounding, not breastfeeding. Better-designed studies find only a handful of real benefits: a reduced chance of severe gastrointestinal infections and a lower risk of eczema during infancy, and perhaps a small boost in childhood IQ.

Alleged Breastfeeding Benefits According to the NHS

According to the NHS, breastfed infants are…

  • less likely to suffer from vomiting or diarrhea and therefore less likely to go to hospital
  • less likely to develop type 2 diabetes in later life
  • less likely to become obese in later life
  • less likely to suffer from heart disease in later life
  • less likely to suffer from constipation
  • less likely to get a chest or ear infection and therefore less likely to go to hospital
  • less likely to suffer from tooth development problems
  • more likely to have good communication and speech skills
  • more likely to have good circulation
  • less likely to suffer from wind, colic and constipation
  • less likely to develop eczema or asthma

Sounds pretty impressive, right? Until you set aside the evidence from observational studies…

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