Tag: microbiome

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.)