Category Archives: Cesareans

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The perils of the virtual world…

Ahem… I’ve just been told that Science & Sensibility is having some spam problems, so apparently my post went up and came down quickly. Should be up again soon. In the meantime here’s the post (below). Check in at Science & Sensibility later to follow any comments that surface, or to further sabotage the site, as you see fit.

And no, I’m not the spammer…

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Unintended consequences: Cesarean section, the gut microbiota, and child health.

When I first learned some years ago that cesarean section was associated with an increased risk of childhood asthma and eczema, I eagerly awaited the rest of the story. What could the link possibly be? Epidurals? Anesthetics? Antibiotics? Something strange and exotic was afoot, I was certain.

Imagine my surprise, then, when a growing body of evidence pointed to an unexpected source: the newborn gastrointestinal tract and the microorganisms that live there.

How might intestinal bacteria play such a major role in the health and well-being of newborns and children? The answer lies in an ancient, mutually beneficial relationship, one that modern birth technology has dramatically altered.

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Some friendly faces…

“Microbiota” is the term used to describe the community of microorganisms—bacteria, viruses, and fungi—that normally live in or on a given organ in the body. There’s a unique microbiota that inhabits the mouth, for example, another that lives on the skin, and still another that populates the intestine, or gut. Given an intestinal surface area of about 2,700 square feet—more or less the size of a tennis court—the microbiota inhabiting the gut is the largest and most diverse in the body.

How large and diverse? The gut microbiota contains roughly one quadrillion cells—at least ten times as many cells as does the human body itself. More than 1,000 bacterial species having been identified to date, with unknown numbers yet to be discovered.

How do all those bacteria get there? The fetal intestine, in the absence of congenital infection, is sterile in utero. The bacteria that come to colonize the bowel are acquired during birth and shortly afterwards, a process that is very much influenced by how a baby is born.

The gut microbiota and mode of delivery

In vaginally-born babies the colonizing bacteria originate primarily in the maternal birth canal and rectum. Once swallowed by the newborn during birth, these bacteria pass through the stomach and upper intestine and colonize the lower intestine, a complicated initial process that takes about a week.

Infants born by cesarean section—particularly cesareans performed before labor begins—don’t encounter the bacteria of the birth canal and maternal rectum. (If a cesarean is performed during labor the infant may be exposed to these bacteria, but to a lesser degree than in vaginal birth.) Instead, bacteria from the skin and hospital environment quickly populate the bowel. As a result, the bacteria inhabiting the lower intestine following a cesarean—the gut microbiota—can differ significantly from those found in the vaginally-born baby.

Whatever the mode of delivery, a core gut microbiota is well established within a few weeks of life and persists largely intact into adulthood. A less stable peripheral microbiota—one that is more sensitive to changes in diet and environmental factors, like antibiotics—is created as well. Between one and two years of age, when weaning from breast milk typically leads to a diet lower in fat and higher in carbohydrates, the gut microbiota takes on its final, mature profile.

Development of the newborn immune system

The dramatic first steps in immune system development take place at the same time the core microbiota is being formed, and the gut bacteria play a key role in that process.

In the hours and days following birth, the newly-arrived bacteria of the gut microbiota stimulate the newborn’s production of white blood

A t-lymphocyte

cells and other immune system components, as well as antibodies directed at unwelcome, disease-causing microorganisms. The bacteria of the microbiota also “teach” the newborn’s immune system to tolerate their own advantageous presence—to differentiate bacterial friend from foe, in other words.

In a cesarean birth the fledgling immune system is confronted with unfamiliar, often hostile bacteria—including Clostridium difficile, a particularly troublesome hospital-acquired bug. In addition, the healthy probiotic bacteria associated with vaginal birth that the newborn’s immune system expects to see arrive later and in lower numbers. These changes in the composition of the normal gut microbiota occur during a critical time in immune system development.

The cesarean-asthma theory (in a nutshell)

Here’s how cesareans and asthma are likely connected:

Humans evolved right along with the gut microbiota normally acquired during vaginal birth. When the composition of that microbiota is imbalanced, or unusual germs like Clostridium difficile appear, the immune system doesn’t like it. A low-grade, long-lasting inflammatory response directed at these intruders begins at birth, leading to a kind of “leakiness” of the intestinal lining. Proteins and carbohydrates that normally would not be absorbed from the intestinal contents—including large food molecules—make their way into the infant’s bloodstream.

To make a very long story short, that inflammation and the abnormal digestion and absorption of food that results appears to increase the risk of asthma and eczema—and diabetes, obesity, and other chronic illnesses—later in life.

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Normalizing the post-cesarean gut microbiota

Reducing the cesarean rate is an obvious best practice in promoting a healthy gut microbiota. But there will always be a need for cesarean section, and so researchers are now beginning to focus on “normalization” of the gut microbiota of cesarean-born babies. Although there are as yet no proven therapies, here are some possibilities:

  • Probiotics. Though administering healthful probiotic bacteria to correct an imbalanced microbiota makes intuitive sense, studies to date have been disappointing. However, research into “good” bacteria and how they become established in the intestine is active and ongoing.
  • Direct transfer of maternal secretions. Placing maternal vaginal and rectal material into the newborn’s mouth has been proposed—more or less mimicking natural colonization—but to date there are no published studies to support the practice.
  • Fecal transplantation. Direct transfer of fecal material from healthy adults into the gastrointestinal tract of people suffering from Clostridium difficile infections has shown promise. Using healthy parents as “donors” for their babies has been proposed, but applying such technology to otherwise healthy newborns is highly impractical at present, to say the least.

Conclusion

A cesarean section doesn’t automatically doom a child to a lifetime of asthma or eczema, just as a vaginal birth isn’t an absolute guarantee of perfect health. But cesarean birth, by altering normal gut microbiota development, does appear to moderately increase the risk of these and other chronic health conditions. A woman who has the option of choosing her mode of delivery should consider this along with the many other factors she must weigh in deciding how her baby will be born.

Mark Sloan M.D.

Selected references:

1)    Effects of mode of delivery on gut microbiota composition

Biasucci G, Rubini M, Riboni S, et al (2010). Mode of delivery affects the bacterial community in the newborn gut. Early Human Development 86:S13-S15

Penders J, Tjhijs C, Vink C, et al (2006). Factors influencing the composition of the intestinal microbiota in early infancy. Pediatrics 118(2):511-521.

Salimen S, Gibson GR, McCartney AL (2004). Influence of mode of delivery on gut microbiota in seven year old children. Gut 53:1388-1389.

2)    Development of the newborn immune system

Huurre A, et al (2008). Mode of delivery: Effects on gut microbiota and humoral immunity. Neonatology 93:236-240.

Johnson C, Versalovic J (2012). The human microbiome and its potential importance to pediatrics.  Pediatrics (published online April 2, 2012; DOI: 10.1542/peds2011-2736).

Vael C, Desager, K (2009). The importance of the development of the intestinal microbiota in infancy. Current Opinion in Pediatrics 21(6):794-800

3)    Cesarean birth, gut microbiota, and asthma/atopic disease

Azad M, Korzyrkyj A (2012). Perinatal programming of asthma: The role of the gut microbiota. Clinical and Developmental Immunology Volume 2012; Article ID 932072; doi:10.1155/2012/932072

Thanvagnanam S, Fleming J, Bromley A, et al (2008). A meta-analysis of the association between caesarean section and childhood asthma. Clinical & Experimental Allergy 38(4): 629-633.

van Nimwegen F, Penders J, Stobberingh E, et al (2011). Mode and place of delivery, gastrointestinal microbiota, and their influence on asthma and atopy. Journal of Allergy and Clinical Immunology 128(5):948-955.e3

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Filed under Asthma, Cesareans, Maternal-child health, Natural childbirth, Obesity, Science

Science & Sensibility, part 2

Science & Sensibility, Lamaze International’s “Research Blog About Healthy Pregnancy, Birth & Beyond,” just posted an essay of mine titled “Unintended Consequences: Cesarean Section, the Gut Microbiota, and Child Health.” It’s an explanation of the probable link between cesareans and childhood asthma, eczema, and other chronic health problems. Stop by and have a read!


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Science & Sensibility

I recently wrote a guest post for Lamaze International’s excellent Science & Sensibility blog. The subject was the study by Huh and colleagues about the association of cesarean birth and childhood obesity. (See my own blog post about the study here.) Interesting discussion going on. Please weigh in if you feel so inclined!

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More on cesareans and obesity

Cesareans? Really?

Does cesarean birth put a baby at increased risk for obesity in the future? Seems a little far-fetched at first glance, but Dr. Susanna Huh and her Harvard colleagues just published a study that makes the link a bit more “near-fetched.” (The study itself is available here.)

Huh’s team found that children born by cesarean section were twice as likely to be obese at 3 years of age than were those born vaginally. This relationship held up even when factors like the mother’s weight, ethnicity, age and how many babies she’d already had  were taken into account. Interestingly, it didn’t make a difference whether the cesarean was performed before or after labor started.

The study wasn’t designed to look at the reasons for the increased risk in obesity, but the Harvard team suggested several possibilities:

The first is the alteration of the gut microbiota–the sum total of all the bacteria found in the human bowel–caused by a cesarean birth. (More detail on that here and here.) This alteration can lead to low-level inflammation in the bowel which is associated with obesity.

The second possibility is that cesarean birth is just a stand-in for something else that’s happening at the same time. In this case, Huh and colleagues wonder about all the antibiotics given to women who are having cesareans. Antibiotics are known to alter the gut microbiota, but research results are mixed as to whether this is a lasting effect.

Finally, it’s possible (though unlikely) that all of this has nothing to do with the gut microbiota. There are hormones and other factors related to inflammation that surge in a mother’s bloodstream (and her baby’s) during labor, and these, obviously, are missing if a mother undergoes a cesarean before she starts labor. The lack of maternal stress response during labor could adversely impact the development of the newborn immune system, leading to the inflammation associated with obesity.

My best guess: it’s a big moosh of all of the above, plus other factors no one has even dreamed of yet. In the meantime, the issue of increased obesity risk is one more thing physicians and pregnant women should consider before deciding on how a baby is to be born.

It’s a complicated matter, this business of hatching healthy humans…

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More on breastfeeding…

As if you needed more reasons to choose breastfeeding, this just in from the journal Genome Biology:

Babies who breastfeed have a wider variety of bowel bacteria than those who are formula-fed. Why is this important? Because the bacteria in the newborn bowel (also known as the gut microbiota) help direct the development of the newborn’s immune system, among the many other beneficial functions they perform. A more diverse gut microbiota is associated with a healthier immune system.

We already know that babies born by cesarean section have a less-diverse gut microbiota than vaginally-born babies, and that following a c-section the newborn gut microbiota is often dominated by bacteria picked up from the hospital environment. Some of those hospital bacteria–clostridium difficile in particular–are associated with a number of nasty diseases in humans. From the looks of this study (and others), formula feeding may exacerbate the problem.

Nature intended for us to have a diverse gut microbiota, dominated by the types of bacteria picked up in the course of a vaginal birth and breastfeeding. We’re only now learning of the long-term health consequences of tinkering with that plan…

PS: In no way am I criticizing women who, for whatever reason, formula feed their babies. Exclusive breastfeeding isn’t always an easy thing to do in this day and age. But however it happens that a baby isn’t breastfed, the potential health impacts are the same.

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Home VBACs on the rise

The rise and fall of VBACs

A new study by Eugene DeClercq and Frances MacDorman–my favorite epidemiologists–looks at trends in home vaginal birth after cesarean (home VBAC) from 1990-2008. The results are interesting, if not surprising, given the trends in American maternity care as a whole.

Basically, Declercq et al found that home VBACs in the U.S., while still rare events, have been increasing–most recently from 664 in 2003 to 1000 in 2008. VBACs accounted for less than 1% of home births in 1996, but are now 4% of total home births. Meanwhile hospital VBACs have decreased from 3% of total hospital births in 1996 to 1% in 2008.

VBACs underwent a steep decline in the late 1990s after the American College of Obstetricians and Gynecologists came out strongly against VBACs being performed in hospitals that did not have 24/7 OB anesthesia services, in case of the need for an emergency c-section. For a small number of women–likely those with no local VBAC alternative–this simply drove VBACs out of the hospital and “underground” – ie, into the home setting.

The safety of home VBACs can (and will) be debated endlessly. The take-home point for me, though, is that this is one more reason to integrate home birth into the larger American maternity care system. Women can’t be forced to give birth in hospitals, and neither demonizing home birth  nor overstating the advantages of hospital birth is doing anyone any good. (For examples of some especially vocal opposition to home birth, see the replies to Dr. Alice Dreger’s article in The Atlantic I cited a few days ago.)

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“The Case for Hospital Births”

Best place to have a baby?

Here’s a kind of counterpoint article, also from The Atlantic,  to the one by Alice Dreger M.D. on low-intervention birth in my previous post. The author, Adam Wolfberg M.D., is an obstetrician at Tufts University who specializes in high risk pregnancies. Right from the article’s first sentence he’s pretty up front about where he thinks births should happen:

“I believe babies ought to be born in a hospital.”

That belief seems to be based on personal experience (I say “seems,” because the only case presented is of a couple who wanted a home birth, ran into trouble that led to transfer, and then were “annoyed” to have had a healthy baby in the hospital) and backed up by a reference to the study by J.R. Wax that purported to show a three-fold increase in infant mortality for babies born at home.

This essay actually offers unintended support to Dr. Dreger’s claim that physicians sometimes confuse science with technology. The Wax study has been heavily criticized for presenting a distorted picture of home birth safety  (details here). Dr. Wolfberg ignores much research to the contrary in picking that particular study as evidence of the dangers of out-of-hospital birth, and his use of a badly flawed study to support hospital birth for all women is exactly the kind of thing Dr. Dreger decries.

As I said in my last post, I’ve been on both sides of this debate. Childbirth is sometimes a scary thing, and it doesn’t always end happily. I’ve seen the kind of birth disasters that make an aggressive approach to childbirth so attractive to physicians, and I’ve also taken care of babies harmed by that style of practice.

The trick is to find a safe balance of nature and technology for each mother and baby. That’s an elusive goal in the increasingly polarized world of American maternity care.

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“The Most Scientific Birth Is Often the Least Technological Birth”

Here’s an interesting article on the science and ethics of American childbirth, from Alice Dreger in The Atlantic. It rings very true.

My career as a pediatrician attending births has been one long tale of learning a lot of stuff and then unlearning quite a bit of it. When I started in the late 1970s we went after even mildly distressed newborns like a medical SWAT team, with laryngoscopes, oxygen masks and umbilical catheters flying, snatching our pint-sized patients from the jaws of…what, exactly? In retrospect, a lot of them would have been just fine without us. Maybe even better off. (And just to be clear, a lot of them really needed the help, too…)

Things have changed remarkably since then. More and more studies support the wisdom of a patient, mother-centered approach to childbirth, though you wouldn’t know it from current epidural, induction and cesarean rates. Some of the refusal to accept what the research clearly tells us has to do with the way new doctors are often still taught to view childbirth: as a dangerous process in need of strict control. From the article:

“Many medical students, like most American patients, confuse science and technology. They think that what it means to be a scientific doctor is to bring to bear the maximum amount of technology on any given patient. And this makes them dangerous. In fact, if you look at scientific studies of birth, you find over and over again that many technological interventions increase risk to the mother and child rather than decreasing it.”

Add in the fact that you’re frequently scared to death as a med student and find technology a comfortable/comforting suit of armor to wear, and it’s not surprising that young doctors often live in fear of normal childbirth. I know…I was there. It only takes one bad outcome to make an aggressive approach look attractive, particularly when that’s the medical culture in which you’re being educated.

Dreger’s article is all the more interesting because she’s a professor of clinical medical humanities and bioethics at Northwestern University’s Feinberg School of Medicine, and her husband is an academic internist–not exactly the stereotype (e.g., the “woman who wears long cotton skirts, braids her hair, eats only organic vegan food, does yoga, and maybe drives a VW microbus,” as Dreger puts it) associated with midwifery and low-intervention births. But when Dreger and her husband did an extensive review of the scientific childbirth literature in 2000 and found that it supported just that–a low-intervention approach–they put what they learned into practice with the birth of their own child.

There’s a place for technology in childbirth, certainly, but most pregnancies don’t need nearly as much of it as they get in the U.S. these days.

Have a read–it’s a great article.

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The Strong Start initiative

"Strong Start" is a good start

The Department of Health and Human Services launched its “Strong Start” initiative yesterday–more than $40 million in renewable grants aimed at reducing preterm births and improving outcomes for newborns and pregnant women.

What makes this initiative different and exciting is that it targets early elective deliveries–that’s right, HHS is out to reduce inductions and cesareans before 39 weeks unless there’s a clear reason to do them, a nod to the complications and expense associated with preterm birth. The initiative also promotes innovative prenatal care practices.

From the Strong Start initiative:

“Reducing the rate of early elective deliveries prior to 39 weeks ensures that more mothers receive safe, evidence-based care, and improves the prospects for good physical and developmental health for infants. It also reduces costs by safely reducing preventable C-section rates, neonatal intensive care admissions and other associated complications.”

In addition to targeting early elective births, the initiative will focus on reducing the rate of preterm births for women covered by Medicaid. Again, from the initiative, this will include:

  • Group prenatal care that incorporates peer-to-peer interaction in a facilitated setting for health assessment, education, and provides psycho-social support.
  • Comprehensive prenatal care facilitated by teams of health professionals including peer counselors and doulas.  Services include collaborative practice, intensive case management, counseling and psycho-social support.
  • Enhanced prenatal care including psychosocial support, education, and health promotion in addition to traditional prenatal care. Services provided will expand access to care, improve care coordination and provide a broader array of health services.

I know, there’s a lot of grant-speak in there–I’ll try to clarify some of that in upcoming posts. But the exciting part is that Health and Human Services (plus a lot of other organizations – see below) is looking to promote programs that go far beyond the way we’ve done prenatal care in the past.

Here’s the roster of groups working together on Strong Start:

This initiative is a joint effort between the Centers for Medicare & Medicaid Services (CMS), the Health Resources and Services Administration (HRSA), the Administration on Children and Families (ACF), and outside groups devoted to the health of mothers and newborns such as the March of Dimes, the American College of Obstetricians and Gynecologists (ACOG), the National Partnership for Women and Families, the Society for Maternal and Fetal Medicine, American College of Nurse Midwives, Childbirth Connection, Leapfrog Group, the National Priorities Partnership convened by the National Quality Forum and others.

More to come…

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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.

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