The importance of microbiota, defined as the community of microbes found in the human body (Pollan p. 2), was overlooked by scientists until recently; However, correlations between the increasing hygiene of the Western world and the increase in chronic diseases such as asthma, have caused scientists to reexamine this community of bacteria. Research now suggests that certain bacteria in the microbiota are essential to human health. As support for this theory increases, researchers have begun to examine the factors influencing the development of the microbiota.
Although research about this development is still a work in progress, there is considerable evidence suggesting that the method of delivery during birth influences the health of the microbiota. In his article, Some of my Best Friends Are Germs, Pollan explains that “most of the microbes that make up a baby’s gut community are acquired during birth — a microbially rich and messy process that exposes the baby to a whole suite of maternal microbes” (p. 4). Unfortunately, all births are not created equally. Caesarean births, which are significantly more sterile than vaginal births, do not allow infants exposure to the same level of bacteria that a vaginal birth would. This explains the higher rates of disorders such as asthma and allergies among C-section babies. Pollan explains that, “not having been seeded with the optimal assortment of microbes at birth, their immune systems may fail to develop properly” (p. 4). Thus, babies born by Cesarean are thought to start life without a fully developed microbiota.
In their primary article, Dominguez-Bello et al put this theory to the test by using gene pyrosequencing to characterize bacterial communities of mothers and their babies. Their research found that the bacteria found in babies were reflective of the bacteria they were exposed to during birth. The article explains that “Vaginally delivered infants harbored bacterial communities (in all body habitats) that were most similar in composition to the vaginal communities of the mothers” whereas “infants delivered via C-section harbored bacterial communities (across all body habitats) that were most similar to the skin communities of the mothers” (Dominguez-Bello et al p. 2). Specifically, samples from vaginally delivered babies had high levels of lactobacillus, prevotella, atopobium, and sneathia spp, four bacteria frequently found in vaginas. In contrast, babies born through C-section had high levels of Staphylococcus spp., a bacteria commonly found on the skin of mothers. These results demonstrate the influence that the birthing method has on the development of the microbiota.
This graph shows how the microbiota of babies is largely a reflection of their method of birth. Vaginally delivered babies have microbiota that resembles the community of bacteria found in their mother’s vagina. Babies born through C-section have microbiota that resembles the community of bacteria found on their mother’s skin. (Source: Dominguez-Bello et al)
In addition, the research by Dominguez-Bello et al showed that “in three of four vaginal deliveries, the mother’s vaginal bacterial community was significantly more similar to her own baby’s microbiota than to the microbiota of other vaginally delivered babies” (p. 2). This suggests that the development of microbiota is affected not only by the method of delivery, but also by the characteristics of the mother. The same is not true for babies delivered via Cesarean, as mothers of C-section babies “were no more similar to their own babies than to the other babies born via C-section” (p. 2). This difference may be due to other skin-level factors, such as the touch of a doctor, that infants are exposed to in the hospital. This lack of resemblance conveys the inability of C-section mothers to transfer microbes during birth.
Overall, the scientists found that “the mother’s vaginal microbiota provides a natural first microbial exposure to newborn body habitats” (Dominguez-Bello et al p. 2 ). Infants who are not born vaginally do not encounter this natural exposure. This lack of exposure may cause long-term issues for the infant, whose bacterial colonization is delayed (Dominguez-Bello et al p. 2). Due to the lack of optimal colonization, Cesarean-born babies are more prone to develop illnesses or disorders.
Unfortunately, Cesarean births are necessary in many cases. Because of this, the question becomes: how do we improve the microbiota of babies born via C-section? Although there may not be a way as effective as coming through the vaginal canal, there are some promising alternatives. One natural option is breastfeeding. As Dominguez-Bello et al explain “breastfeeding has been suggested to enrich vaginally acquired lactic acid-producing bacteria in the baby’s intestine” (p. 2). Breast milk is considered a probiotic, meaning in introduces new microbes into the body (Pollan p. 4). Another way to improve the microbiota of infants is to give them probiotics in the form of pills for a period of time. These alternatives may allow mothers who are forced to deliver via Cesarean to feel at peace about their babies’ health. Future research will be necessary to determine if these alternatives can compare to the effectiveness of vaginal birth in developing the microbiota.
Because fetuses are thought to develop in a bacteria-free environment, their exposure to bacteria begins upon delivery. This exposure differs based on the method of birth. Research suggests that Cesarean-born babies are not exposed to the same quantity and quality of positive bacteria as vaginally delivered babies are. Dominguez-Bello et al convey this theory in their research by analyzing the microbiota of babies as compared to their mothers. They found that babies born vaginally have high levels of the bacteria that is commonly found in a woman’s vagina and is specific to their mothers. In contrast, C-section babies have high quantities of skin-level bacterias that are not specific to their mothers. The lack of microbe diversity in Cesarean-born babies may explain their increased susceptibility to sickness and disorders.
Sources:
Dominguez-Bello et al http://www.pnas.org/content/107/26/11971.abstract
Pollan http://www.nytimes.com/2013/05/19/magazine/say-hello-to-the-100-trillion-bacteria-that-make-up-your-microbiome.html?pagewanted=all&_r=0
Ecological and Evolutionary Medicine 
This sounds like a very interesting follow up article relating to the Pollan article. The question I kept asking myself while reading this blog post was this: What are the statistics and exact percentages of babies who have developed these diseases and disorders after a Cesarean birth? Personally, I’ve never heard of serious side affects to a C-section. In fact, my younger brother, for instance, was birthed through the operation of Cesarean. He never developed any sort of disorder or infection. Is it a possibility that he had already developed these microbes, similar to babies born vaginally, within the womb? I am assuming that microbes are different in all babies. Is it possible that they develop similar microbial environments before they are birthed? Whitney briefed on the suggestion that not only is the method of delivery essential to the development of microbes, but the characteristics of the mother, as well. I find this interesting because not all babies that are delivered through a C-section develop some kind of disorder. In fact, I thought this method of child birth was safer than a vaginal delivery.
My overall question, however, is what exactly are the risks of a C-section? What kind of disorders or diseases are probable through this method?
I am not sure of the answers to all of your questions, but I do know that the article said that babies in the womb are considered to be free of any microbes. This means that according to the research that we have so far, babies could not develop microbes similar to those in vaginally-born babies while in the womb. I too was a c-section and have no allergies or disorders, which is why I found this topic so interesting. However, my theory is that if babies are breastfed, as I was, they may be able to develop a healthy microbiota despite the lack of vaginal bacteria. Perhaps this is why your brother is healthy as well?
I also did my Pollan follow up post using this article. I think from the microbe standpoint, the main risk with C-section is that the babies do not completely receive the most pure form of microbes from their mother. I also thought of breastfeeding as a solution. But by consuming milk, does it have the same effect as direct contact with vaginal microbes? Also, some babies are breastfed for a longer period of time that others. Does this mean that the ones fed for a shorter time period would have weaker immune systems because they aren’t ingesting as much milk with gut microbes?
This article talks about breastfeeding in comparison with using formula, and breastfeeding is clearly the better option between the two for a baby’s health. But what about breastfeeding vs. the microbes that are found naturally from vaginal birth? Also, if a baby is birthed naturally and breastfeeds, would it make them “extra immune”?
http://www.sciencedaily.com/releases/2012/04/120429234641.htm
There was one part of this post that stuck out to me the most, “Infants who are not born vaginally do not encounter this natural exposure. This lack of exposure may cause long-term issues for the infant, whose bacterial colonization is delayed.” It makes sense that not encountering natural exposure would cause long term issues for an infant. However, my mind went in another direction to babies who are put in incubators. Babies are put in for good reason, many because they are premature and too young to encounter the world and be able to protect themselves from outside germs and survive. Premature babies are extremely weak and in some cases premature babies come out just after they are able to survive life outside of the mom’s womb. To my understanding incubators exists to keep the child in an environment where there are little or no connections to the outside world. In most cases parents are also unable to touch their babies (unless wearing gloves and even there that is extremely rare), though they are allowed in the room to sing and talk so that the baby can have some form of connection with people. Though I know that incubators are the best current option for a premature baby to have life, I wonder what this does to their microbiome. Does it just delay the baby from developing more microbiota from the parents, specifically the mother if they were born through their mothers’ vagina? What if the baby was born via C-section and was premature and put into an incubator. Does this once again just delay access to vitally important microbiota or does it do more than that? I wonder what lack of exposure to the world and microbiota do for premature babies.