When a mother gives birth vaginally and if she breastfeeds, she passes on colonies of essential microbes to her baby. This continues a chain of maternal heritage that stretches through female ancestry for thousands of generations, if all have been vaginally born and breastfed.

This means a child’s microbiome, that is the trillions of microorganisms that live on and in him or her, will resemble the microbiome of his/her mother, the grandmother, the great-grandmother and so on, if all have been vaginally born and breastfed.

This transgenerational microbial legacy begins in pregnancy.

To use an analogy, pregnancy sets the conditions for a big party to take place in the baby’s gut. This once-in-a-lifetime event is open to everyone, but especially welcome are the VIP guests, the mother’s vaginal, gut and breast milk microorganisms.

During pregnancy, the baby is mostly protected from harmful microorganisms by the amniotic sac, but recent research suggests the baby could be exposed to small quantities of microbes from the placenta, amniotic fluid, umbilical cord blood and fetal membranes. One theory is that any possible prenatal exposure could ‘pre-seed’ the infant microbiome. In other words, to set the right conditions for the ‘main seeding event’ for founding the infant microbiome. 

As soon as the mother’s waters break, this is the moment the party doors swing open, the stereo is switched on and the first VIP party guests flood in. Suddenly the baby is exposed to a wave of the mother’s vaginal microbes that wash over the baby in the birth canal. They coat the baby’s skin, and enter the baby’s eyes, ears, nose and some are swallowed to be sent down into the gut. More VIP guests in the form of the mother’s gut microbes join the colonisation party through contact with the mother’s faecal matter. Many more microbes come from every breath, from every touch including skin-to-skin contact with the mother and of course, from breastfeeding.

Inside breast milk, you have special sugars called human milk oligosaccharides (HMO’s) that are indigestible by the baby. These sugars are designed to feed the mother’s VIP microbes newly arrived in the baby’s gut.

The HMO’s feed the party guests, fuelling the party spirit, so that the microbes quickly multiply. By multiplying quickly, the ‘good’ VIP bacteria crowd out any potentially harmful gate-crashing pathogens. These ‘good’ bacteria help train the baby’s naive immune system, teaching it to identify what is friend to be tolerated, what is pathogen to be attacked. In other words, the mother’s bacteria teach security who to keep in the party, and who to eject. If the party gets off to a great start, and the chain of maternal heritage continues, this leads to the optimal training of the infant immune system resulting in a child’s best possible lifelong health.

With C-section and formula feeding, the baby is not likely to acquire the full complement of the mother’s vaginal, gut and breast milk microbes. Therefore, the baby’s microbiome is not likely to closely resemble the mother’s microbiome. A baby born by C-section is likely to have a different microbiome from its mother, its grandmother, its great-grandmother and so on. C-section breaks the chain of maternal heritage and this break can never be restored. From that moment on, a different set of microbes will be passed on to that child’s child, to that child’s grandchild, and great-grandchild and so on.

Returning to the party analogy, there’s a different crowd at the gut colonisation party with a baby born by C-section. You’ll still have the party guests coming from the air and from every touch, but at least with elective C-section, you won’t have the VIP party guests from the mother’s vagina and gut. (With emergency C-section, there might be some exposure to the mother’s vaginal microbes during labor if the waters have broken prior to surgery.)

In nine recent cohort studies,* the microbial profiles of babies born by C-section have a lower abundance of the species Bacteroides than vaginally born babies. A very recent study published by Chu. D et al., in Nature Medicine 2017, also shows this lower abundance of Bacteroides in their cladograms and heatmaps, but the researchers chose not to report this data in numbers.

What does an altered microbiome mean for a child’s lifelong health? Causation is still to be proven, but many studies link C-section with a significantly increased risk for developing asthma, Type 1 diabetes, celiac disease and obesity.

With formula feeding, the baby won’t receive the 700 species of microbes found in breast milk. The baby also won’t receive the human milk oligosaccharides that provide the perfect food to feed the microbes newly arrived from the mother‘s vagina and gut (if vaginally born). Plus, formula milk is likely to contain other bacteria that are not supposed to be there, for these might interfere with the optimal training of the immune system, with consequences for a child’s lifelong health.

Over the past five years, through co-directing the award-winning documentary MICROBIRTH and through co-authoring the book, YOUR BABY’S MICROBIOME, I’ve interviewed dozens of world-leading professors about their research. Scientists might not yet have all the pieces, but the picture that is forming is that C-section and formula feeding could be significantly impacting the health of the next generation. Through the transgenerational aspect to birth, it could even be impacting the health of future generations.

In other words, we risk breaking the chain of maternal heritage at our peril.

References

*Nine Cohort studies showing consistency of low abundance of Bacteroides for babies born by C-section: Jakobsson et al. 2014, Azad et al. 2016, Hesla et al. 2014, Backhed et al. 2015, Penders et al. 2013, Madan et al. 2016, Dogra et al. 2015, Martin et al. 2016, Yassour, et al. 2016

The Completed Self: An Immunological View of the Human-Microbiome Superorganism and Risk of Chronic Diseases. Dietert, Rodney R., and Janice M. Dietert. Entropy 14 (2012): 2036–65, doi:10.3390/e14112036.

The Infant Microbiome Development: Mom Matters Noel T. Mueller, Elizabeth Bakacs, Joan Combellick, Zoya Grigoryan, and Maria G. Dominguez-Bello, Trends in Molecular Medicine 21, no. 2 (January 8, 2015): 109–17, doi:10.1016/j. molmed.2014.12.002.

The Placenta Harbors a Unique Microbiome Kjersti Aagaard, Jun Ma, Kathleen M. Antony, Radhika Ganu, Joseph Petrosino, and James Versalovic, Science Translational Medicine 6, no. 237 (May 21, 2014): 237ra65, doi:10.1126/ scitranslmed.3008599.

CHILD Study Investigators. Impact of maternal intrapartum antibiotics, method of birth and breastfeeding on gut microbiota during the first year of life: a prospective cohort study. Azad MB , Konya T , Persaud RR , Guttman DS , Chari RS , Field CJ , Sears MR , Mandhane PJ , Turvey SE, Subbarao P , Becker AB , Scott JA , Kozyrskyj AL , BJOG : an international journal of obstetrics and gynaecology. 2016; 123(6): 983-993.

Maturation of the infant microbiome community structure and function across multiple body sites and in relation to mode of delivery Derrick M Chu, Jun Ma, Amanda L Price, Kathleen M Anthony, Maxim D Seferovic & Kjersti M Aagard, Nature Medicine (2017) doi:10.1038/nm.4272

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

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