Category Archives: Natural childbirth

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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

A closer look at “term” birth

Of baby brains and reading scores…

When I was in my pediatric residency I was taught that a baby born between 38 and 41 weeks was “full term.” Babies born in that golden four weeks were thought to be one homogeneous group in terms of future development. A baby born at 38 weeks gestation was home free, at least as far as his neurological future went.

Not so fast. A study of more than 100,000 New York children just published in the journal Pediatrics reports that those born at 38 weeks–the low end of the term age bracket–in general don’t perform as well on standardized tests of math and reading in third grade as do children born later in pregnancy.

And not only that:

Each week of increased gestation from 37 to 41 weeks showed an added benefit in both reading and math scores. Further, children born at 37 or 38 weeks performed significantly worse than children born at 39, 40, or 41 weeks, and have a significantly increased relative risk of impaired reading and math skills on standardized school achievement tests.

The brain grows rapidly between 38 and 41 weeks gestation: gray matter increases nearly 50%,  and myelinated white matter triples as the brain increases in complexity. It’s not surprising that being born even two or three weeks early might negatively impact some babies.

The study isn’t perfect, and it’s best to keep in mind that increased risk doesn’t equal inevitablility–the large majority of babies born at 38 weeks will be just fine. Still, researchers in Denmark, Belarus, Switzerland, and Scotland have recently reported findings similar to those in the New York study–all of which supports the growing effort to reduce elective, early labor induction.

Best to leave babies in the womb until nature says it’s time to come out!

 

 

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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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Finger foods help prevent obesity

Filthy, yes. Fat, no.

Here’s something I’ve always felt made sense: Babies allowed to wean themselves to finger foods when they’re ready are less likely to become obese than those who continue to be exclusively spoon-fed. The simple explanation: it’s easier to learn to quit eating when you’re full if you’re the one controlling the feeding. In my experience the finger feeding phase arrives between 6 and 12 months, right at the age babies start fighting spoon feedings. (They must be reading the studies!)

Fear of choking is the concern I hear most often from parents leery of letting their babies finger feed themselves. But think of the foods typically offered as finger foods: cereal puffs, cheese, soft-cooked peas and carrots, and such. These are nearly impossible to choke on, since they quickly stick to saliva (and hair, and eyelashes, and nostrils, etc.). I challenge you – put a Cheerio in your mouth and try, try to inhale it and choke on it. You can’t, and neither can your baby.

The dangerous foods are slippery ones. Every year the leading causes of choking deaths from food are hot-dog chunks (with the skin all the way around) and whole grapes. (This usually happens to toddlers, who can grab food for themselves, and not infants, who eat what they’re given.) This is because the skin or peel makes it easy for the food object to slide to the back of the throat and block the windpipe.

Keep in mind, too, that choking and gagging are actually two very different things. Choking occurs when a solid object blocks the flow of air through the windpipe. Gagging moves food forward and away from the windpipe, and so actually protects babies from choking. It’s a good idea to take an infant CPR course so you’ll know the difference and be prepared in case of a real emergency. Most local hospitals and Red Cross chapters offer such classes.

Still, if your baby gags easily, go easy on the finger foods until a bit later. You want mealtime to be positive, and as we all have experienced at one time or another, gagging is not a pleasant sensation. The easy-gagger phase will pass in time.

In the meantime, on to finger feeding (and a jumbo under-the-high-chair ‘splat mat’!)

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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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Delayed cord clamping: Settling the debate

"Told you so!"

Aristotle was on to something, way back in the B.C.’s, when he wrote approvingly of the midwifery practice of not cutting the cord until the placenta was delivered.

He was also struck by the midwives’ practice of “stripping” the umbilical cord in emergencies: forcing the blood remaining in the umbilical cord back into a newly born baby in need of reviving. 

‘‘Frequently the child appears to be born dead, when it is feeble and when, before the tying of the cord, a flux of blood occurs into the cord and adjacent parts. Some nurses who have already acquired skill squeeze (the blood) back out of the cord (into the child’s body) and at once the baby, who had previously been as if drained of blood, comes to life again.’’

For Aristotle and centuries of midwives, cord clamping was a thing best done slowly.

Clamping the cord: early or late?

In the 1970s western hospital-based medicine abandoned the practice of “delayed” cord clamping*–that is, waiting until the cord stops pulsing to cut it.  In an effort to decrease postpartum hemorrhage, “early” clamping–cutting the cord as soon as possible–became the norm. But new research now proves that, as far as umbilical cords go, the old way is still the best.

Researchers in Sweden recently showed that delayed clamping is not only safe, it’s highly beneficial to babies. In a world in which iron deficiency damages the brains of millions of children a year (including here in the U.S. – more on that in a later post), delayed clamping allows more iron-rich blood to pass from the placenta to the baby at birth.

The Swedish researchers found that all measures of iron metabolism were improved in four month-olds who were treated with delayed clamping. No complications or side effects were noted. 

It’s time for hospitals to re-adopt delayed clamping as standard procedure, just as nature intended.  To borrow another Aristotle-ism, “Nature does nothing without reason or in vain.” Amen.

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*(“Natural” would be a better term than “delayed”, seeing as that’s when nature chooses to close down the blood vessels in the cord. But I don’t get a vote on these things, so we’ll go with “delayed.”)

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Movie star has vaginal birth: India agog

I don’t know whether to cheer or cry at this one.

News flash: "Old" lady has a baby.

Bollywood star and former Miss World Aishwarya Rai gave birth to a healthy baby girl last week. Her “feat” of doing so vaginally created an immediate sensation across India, proving, as the Times of India put it:

“One is never too posh to push or too old for a natural delivery.”

Never mind that Ms. Rai just turned 38 this month. It actually is remarkable that she chose vaginal birth in a country where the cesarean rate for women over 35 is around 60%, and that cesarean rates of 80% and more are common for women of all ages in many private hospitals.

In the same article the Times gives this straight-outta-the-19th-century rationale for why so many modern Indian women choose a cesarean:

“Studies have shown that today’s woman with her low threshold for pain is more likely than her mother to opt for a C-section.”

Oy.

Why women "choose" cesareans.

The Times goes on to describe an “Aishwarya Rai Effect”–many more young women are expected to choose vaginal birth as a result of her choice.

Now if we could just line up some “posh” American celebrities to “push” for vaginal birth, we might counteract the “Britney Spears Effect” and put a dent in our own cesarean rate.

Too bad Justin Bieber‘s not a woman…

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Michigan: Doing something about high cesarean rates

Very intriguing study coming out of Michigan.

Preliminary results from the Michigan Health and Hospital Association Keystone obstetrics project, which involves 65 hospitals–including most of the state’s major birth centers–show that the project so far has been very successful in reducing unnecessary cesarean sections.

The Keystone project discourages elective or scheduled sections, and the use of labor-inducing drugs, before 39 weeks gestation unless a woman is having a pregnancy complication that necessitates an early delivery. The results are encouraging:

Way to go, Wolverine State!

In the U.S., the C-section rate hovers at about 32% of all births. In Michigan, it was 34% in 2008, the latest year for which figures are available. He said Oakwood has succeeded in getting C-section rates down to 27% at its South Shore Medical Center in Trenton and its Annapolis hospital in Wayne, and 30% at Oakwood in Dearborn, where the C-section rate is higher because it sees more high-risk patients.

Breaking the data down a bit more:

Early data show elective C-sections before 39 weeks of pregnancy fell to 6% from 24% of all births [compared with 2008], and use of labor-inducing drugs dropped to 7% from 20% of all births, according to data collected from March 2010 to March 2011.

Not only that, but there were fewer babies admitted to neonatal ICUs, and Apgar scores, which measure a baby’s adaptation to life outside the womb in the first five minutes of life, were significantly higher as well.

If the preliminary results are borne out by the final study (yet to be published), Michigan will hopefully lead the way in changing how childbirth is managed in American hospitals.

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