Microbirth: What It Is And Why You Should Know About It

Written by

Jessica Williams

9:00 am
08/11/17

Right now, about 100 trillion microscopic living organisms are wriggling around in and on your body, making themselves at home. But no need to panic and reach for the antibacterial hand wipes. These itty-bitty organisms, called microbes, are supposed to be there.

Collectively, this community of microbes—organisms such as bacteria and viruses—forms your microbiome, a delicate, diverse ecosystem that protects you from disease, produces vitamins, and even helps regulate your metabolism. But, alarmingly, the diversity of this microbiome is diminishing, which is dangerous since diversity protects us against “bad” bacteria, or pathogens. And scientists speculate this lack of diversity might be contributing to the rise in noncommunicable diseases such as asthma, diabetes, and obesity.

So, what’s causing this shrinking diversity? Multiple factors may be to blame, including widespread antibiotic use, antimicrobial substances (those hand wipes), and, perhaps, C-sections. To explain: some scientists hypothesize that birth, along with breastfeeding and skin-to-skin contact, plays a critical role in the “seeding” or establishing of this delicate ecosystem, so much so that the way a baby is born (that is, the mode of delivery, whether caesarean or vaginal) may affect how that baby’s microbiome is established, which could affect how that baby’s immune system develops and matures.

This is all illustrated in Microbirth, the fascinating, award-winning 2014 documentary by Toni Harman and Alex Wakeford, which explains that during a vaginal birth, gut bacteria is passed along to the next generation. Scientists believe certain bacterial species collect in a mother’s breasts and vagina during pregnancy then, during labor, the bacteria is transferred from mother to baby in the birth canal. “As the baby starts going out through the birth canal, the baby is acquiring the mother’s bacteria from the mother’s vagina. The baby is coated in the bacteria and swallows the bacteria. This is the baby’s first introduction to the world of bacteria… That’s the founding microbiome for that baby,” says Dr. Martin J. Blaser, M.D., Director of the Human Microbiome Project at New York University, in Microbirth. And some scientists believe babies have just this one shot at birth to seed their microbiomes correctly so the microbiome is fully functional, which is why vaginal delivery, along with breastfeeding and immediate skin-to-skin contact, is so important—because microbes are transferred from mom to baby in all of those instances.

But what about babies who bypass the birth canal, babies born by often lifesaving C-sections? Researchers found that birth by C-section, exposure to antibiotics, and formula feeding slow the development and decrease the diversity of a baby’s microbes through the first year of the baby’s life, as published in a June 2016 study in the journal Science Translational Medicine. “Our results provide evidence that modern practices change a baby’s microbial communities in ways that last through the first year,” says Blaser, the study’s senior author, in a press release.

But the big question is how—or if—this microbial change affects a baby, long-term. “The big, remaining question is whether or not changes in this timeframe, even if resolved later on, affect the founding of microbiomes with lifetime consequences for a child’s immune function and metabolism,” says Blaser. For instance, could these microbial changes affect how susceptible that baby is to infection and to noncommunicable diseases, such as asthma, allergies, Type 1 diabetes, obesity, cardiovascular disease, and celiac disease, later in life?

Studies are ongoing and include a February 2016 study in which researchers at New York University Langone Medical Center were able to partially restore the mix of bacteria that coats a baby’s body when delivered vaginally by “swabbing” C-section babies with their mother’s birth fluid (referred to as “vaginal seeding”). To do this, “researchers incubated sterile gauze in the mother’s vagina during the hour before the C-section, and used it to swab the baby’s mouth and body within two minutes of birth,” according to a press release. (Side note: This is not standard procedure during a cesarean delivery. Doctors have advised against “doing it yourself” for reasons explained here).

But not all researchers agree that mode of delivery affects the baby’s microbes. Rather, events throughout pregnancy or the underlying reasons for the C-section—not the surgery itself—could drive the microbiome variations. For instance, a maternal high-fat diet has been linked with a baby’s microbiome variations at birth, as discussed in a November 2016 review article in EMBO Reports.

In fact, in a January 2017 study, researchers at Baylor College of Medicine found that, when looking at four- to six-week-old babies and controlling for underlying reasons for the C-section and other factors like mom’s antibiotic use, mode of delivery did not affect the babies’ microbiome composition. “When we applied general linear models to control for confounders and looked at infants at 4 to 6 weeks of age, we could find no evidence that there was a difference in the microbiome composition between cesarean and vaginally born babies,” says Dr. Kjersti Aagaard, M.D., Ph.D., Professor of Obstetrics and Gynecology at Baylor University and maternal-fetal medicine specialist at Texas Children’s Hospital, in a press release. “It is incredibly important to answer this question accurately, not only because more than 1 million babies a year are born via cesarean section, but also because any future interventions aimed at correcting or mediating an altered microbiome of cesarean born babies needs to be targeted to the correct window of time. We perform cesarean deliveries every day for really good reasons, and we need to be cautious that we do not assign risk to the wrong source, or misattribute risk to a surgery itself rather than the underlying reason that the surgery was undertaken,” she says.

Clearly, there’s much debate. Dr. Dana R. Gossett, M.D., Professor of Obstetrics and Gynecology at the University of California, San Francisco (UCSF), whom we spoke with previously about C-sections, and who is not involved in the studies, explains there’s not a ton of research on this subject although there’s a lot of interest in it. “There’s some research that demonstrates that children born via cesarean have different gut flora than babies who are born vaginally. And that is pretty credibly settled,” she says. “What’s not totally clear is what the implications are and whether that’s really what drives differences in things like allergies.” And it’s unclear whether vaginal seeding affects a baby long-term, either. “It’s not clear that the procedure of vaginal seeding does anything that has any long-term meaning,” says Gossett.

Certainly, the research is ongoing, and it’s something to watch. Interested in learning more? The directors of Microbirth published Your Baby’s Microbiome: The Critical Role of Vaginal Birth and Breastfeeding for Lifelong Healthcare earlier this year, and they’re working on a new documentary to be released this summer on the connection between gut bacteria and human health with a focus on the early years. Stay tuned!

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