How Birth & Breastfeeding Affect the Infant Microbiome

Having grown for nine months in mother’s nearly sterile womb, a baby is born with essentially no microbiome and an immature immune system. Most newborns get their first exposure to microbiota from their mother during the vaginal delivery, while traveling through the birth canal.

What is the microbiome? It is collectively the ecosystem of trillions of microorganisms living on and in the human body, which play a massive role in the immune system and health outcomes throughout a person’s lifespan. These microorganisms (also known as microbiota) carry out their function by influencing immunologic, endocrine, and neural pathways. At the time of birth, these bacterial microbes from mother’s birth canal spread to the newborn’s skin, digestive tract, urogenital tract, and respiratory organs.

When baby is covered with mother’s microbiota in a vaginal delivery, the newborn’s gut microbiome begins to develop, versus a baby born by cesarean delivery. An infant born by vaginal delivery will naturally receive microbes from their mother’s birth canal, but an infant born by planned cesarean section will be exposed to mainly microbes from mother’s skin and hospital environment, which impacts baby’s microbiome development. However babies born to mothers who labor vaginally for an extended time, but end up requiring cesarean section, may be exposed to the microbiota in the birth canal.

Recent studies suggest that babies whose microbiome development is disrupted by factors such as a cesarean section delivery, early antibiotic use, or limited or no breastfeeding, are at greater risk for a multitude of health issues, including asthma and allergies, respiratory infections, irritable bowel disease, type 1 diabetes, and obesity. Though still controversial, some researchers have been studying whether a practice for newborns delivered by cesarean section, called “vaginal seeding,” in which a cotton swab is used to inoculate baby’s skin, nose, and mouth with fluids from mother’s birth canal, may be helpful for establishing a healthy microbiome in these babies. Moreover with every cesarean section, skin to skin contact between mother and baby immediately after delivery and exclusive breastfeeding are still beneficial.

No matter how a baby is delivered, the newborn’s nutrition sets up the microbiome. Breastfeeding is the most important way to support a baby’s microbiome. Breast milk is a complex fluid capable of satisfying all the nutritional requirements of a newborn and provides health benefits, such as reduced risk of various infections. Additionally breast milk contains many non-nutritional factors such as lactoferrin, secretory immunoglobulin, oligosaccharides, interleukin-10, and other inflammatory mediators, which may play key roles in the inflammatory response to bacteria in the gut. Important too is that breast milk composition changes over the period of lactation, adapting to the requirements of the infant.

Breast milk is one of the main factors that influences the infant microbiota because breastfeeding increases the number of Bifidobacterium, which is one of the first microbe colonizers of the infant gut. Bifidobacterium breve (B breve) is a bacterial species found in the human intestine. It’s especially relevant in early life, being one of the most abundant bacteria in the newborn gut, and is key in development of a healthy gut and immune system. Some of the benefits associated with B breve include protection against microbes causing infection or disease, interacting with immune cells and modifying immune responses, and provision of nutrients through the breakdown of non-digestible carbohydrates from the diet that the infant gut cannot digest. One specific component of breast milk that affects the composition of the microbiome is human milk oligosaccharides (HMOs), which are the most abundant carbohydrates present in breast milk after lactose, and serve as food for key beneficial bacteria. These carbohydrates cannot be digested by the baby’s gut, which is where B breve plays an important role. B breve is among the microbes that can breakdown human milk oligosaccharides, and consequently, promote its persistence in the gut.

Interesting research continues and evidence has shown that starting from birth to approximately three years old, the gut microbiome develops and completes colonization of a diverse and abundant spectrum of microorganisms, which may result in a gut in healthy (eubiosis) state or unhealthy (dysbiosis) state for individuals throughout their lifespan. It’s amazing that the human body develops its own vital microbiome which may determine future health outcomes, and to think, it all begins from delivery of baby into the world through the birth canal, mom holding baby skin to skin after delivery, and exclusively breastfeeding!

Learn more for yourself from the plethora of information, research articles, and books about the human microbiome that are out there. Here’s a recommended book to take a look at, “Your Baby’s Microbiome: The Critical Role of Vaginal Birth and Breastfeeding for Lifelong Health” by Toni Harman and Alex Wakeford: https://amzn.to/3vh1r5I

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