We turn now to another area of emerging science which like epigenetics, investigates the long-term effects of birth experience on newborn development. In particular, the relationship between interventions around the time of birth and early progression of the infant microbiome. This research investigates the role that the human microbiome plays in normal growth and development following birth, especially in regard to immune and metabolic functioning. What do we know about the newborn microbiome? We know that we as humans maintain a symbiotic relationship with trillions of bacteria that colonize all different parts of our body. That birth, and the newborn period, represent an important early colonization and development process. We know that while microbial colonization may begin in utero, the first massive exposure occurs at the time of vaginal birth when babies are exposed to their mother's vaginal, fecal and skin bacteria. Initially, the newborn microbiome is undifferentiated across sites. That is, for example, the bacterial profile of different body habitats like the intestine, the skin, and the mouth are very similar and they tend to match their mother. It is only later after the first year or two that these colonies begin to differentiate more like what we see in adults. Initial colonization, the newborn gut with normal bacteria, is key to maturing immune response, competing with or displacing possible pathogens, supporting digestion and nutrient absorption, and regulating metabolic function. Interventions at the time of birth had been associated with microbiome alterations in the newborn and in turn is alterations have been associated with health outcomes later in life. These outcomes include such things as asthma, allergy, celiac disease, Crohn's disease, irritable bowel syndrome, ulcerative colitis, eczema, type one diabetes, and obesity. The majority of research in this area has investigated the effects of delivery mode that is comparing vaginal delivery with caesarian delivery. Also looking at exposure to antibiotics versus no exposure. Then feeding method, that is whether the baby is fed with breast milk or with formula. My own research in this area also compared infants who were born at home to infants born without intervention in the hospital. For most of human history, after all, babies have been born in home-like environments. Hospitalization for birth is a relatively recent development on an evolutionary scale. The outcome that is measured in this research, is usually fecal microbiome composition or the level of alteration. To review how these interventions might affect the microbiome, with caesarian section, we can see that a baby delivered operatively has more limited contact with maternal, vaginal, and fecal bacteria. Given that it does not pass through the birth canal. Antibiotics are also typically given at the time of caesarian section. Depending on the hospital, mother and baby may be separated after birth. This is increasingly irrelevant as the rate of caesarian section climbs globally. Research suggests that antibiotics may also alter the newborn microbiome, whether these antibiotics are administered directly to the baby or the baby receives them through secondary exposure, via maternal treatment. Well, we depend on antibiotics, of course, to combat pathogens, there can also be collateral damage when beneficial bacteria is killed or suppressed. There's also a significant body of research investigating the effects of feeding method on the newborn microbiome. The microbiome of formula fed babies may differ due to the lack of ongoing contact with maternal skin and milk, microorganisms, and the lack of breast milk components like oligosaccharides, that promote microbial growth. Finally, research investigating home birth has limited, as mentioned, my own study and a large study of around 1000 women conducted by ponders and colleagues in the Netherlands in 2006 found that babies who delivered at home had the most beneficial microbiome. A predominance of more normal colonizers. More research is needed to identify the factors that contribute to this difference. But it's interesting to consider environmental differences, such as the very clean, sometimes near sterile environment created in the hospital, or common hospital practices like bathing the infant shortly after birth, limiting mother and baby contact, etc. These practices are so common, we often don't even think of them as interventions, but collectively, they may still impact exposure for the baby. There's still much more to come in this area, for example, research that investigates bacterial restoration following caesarian section, other influences that shape the newborn microbiome, like variations by geography, cultural practices, lifestyle and diet. However, taken collectively, this research supports the importance of birth practices. Such as those that are foundational to midwifery care that promote and protect undisturbed birth. This research points toward using interventions as medically needed, but not electively and without medical reason as an important means to give babies and their microbiomes the best start in life.
