Bringing my daughters into this world was quite an unforgettable experience. I had a lot questions and uncertainties prior to giving a birth for the first time so I took birthing workshops, pregnancy yoga classes, and a lactation workshop to prepare myself better for what was going to happen. These preparations certainly gave me some degree of confidence, yet looking back I feel like there was still something missing. Everybody kept elaborately telling how the baby goes through the birth canal and how to push, but nobody mentioned anything about the importance of the surrounding microorganisms in the first minutes, days, weeks of a newborn’s life.
As governed by Mother Nature, babies acquire their first significant dose of microorganisms from their mothers during the birth. Bacteria colonize the newborn’s every surface, including their skin and the mucosal membranes of the digestive tract, respiratory tract and urogenital tract. This population of microorganisms (microbiota) remains with us from birth to death, helping us maintain balance by constantly responding and adjusting to internal and external factors. Learning more about human microbiome, in infancy and through the lifespan, can help answer some fundamental questions, such as its importance in our health and disease.
Interestingly, the most recent findings contradict the common belief that the healthy maternal womb is a sterile environment, and that the fetus is not colonized with bacteria until the birth. Thus, the new studies have found commensal bacterial species in placenta, amniotic fluid and fetal meconium, suggesting that the microbial acquisition actually happens before the birth. During the 3rd trimester of pregnancy, as the fetus matures it swallows more amniotic fluid, and this is probably the first manner of contracting microbes. In support of this hypothesis, the results of one study found shared bacterial species from the amniotic fluid in the meconium of neonates. The first microbes occupying the newborn’s body create a complex and life-long relationship with the newborn. The early-life gut microbes are believed to stimulate the development of the immune system, the establishment of healthy digestive function, gut motility, immune tolerance to foods and various antigens, and defense against pathogens. As the baby grows, it is constantly exposed to various microbes through contact with people, new foods, animals, exposure to medicines, and all these experiences contribute to a unique and individual microbial finger print for each and every human. The first 3 years of life are critical for the neurological, immunological and metabolic development of a child, as well as for the establishment of the microbial gut microbiota. This is the time when the foundation is laid that will play a role in our health in the future. At the age of about 3 years, the gut microbiome resembles an adult microbiome.
What if the baby is born by C-section?
The C-section originates from Roman times, when it was introduced to save the baby’s life, the mothers always died. Nowadays, the C-section procedure saves the mothers’ lives as well, but it has also become such a routine procedure that some mothers and/or physicians decide to deliver the baby this way out of convenience. Does the mode of baby delivery affect the infantile gut microbiota? It actually does, infants born vaginally colonize bacteria found in the maternal vagina, such as Lactobacillus and Prevotella. Whereas, C-section delivered newborns will be home for microbes found on the skin, typically including Staphylococcus, Clostridium, Propionobacterium, and Corynebacterium species. As a result, they have lower numbers of anaerobic (requiring no oxygen for growth) microorganisms of Bacteroides and Bifidobacterium commonly found in vaginally born infants. So as a result, we can see that having a C-section, to some extent, deprives babies of their naturally occurring, naturally evolved and selected vaginal microflora. So in the end, what is the price the infant will pay when born by a C-section? Well, there is still more research needed to provide clear answers, but I believe that it undoubtedly influences the individual’s gut microbiome, and therefore may have long-term consequences on gut function and even health. The microbial acquisition, in concert with other factors, within the first week of life sets a ground for the composition of the baby’s future gut microbiota. I appreciate that Dutch midwives and Dutch health care promote and encourage natural birthing, as this practice plays an extremely important role in preserving our precious microorganisms.
The breast milk influences infantile gut microbiota
It’s always been said that breast milk is the optimal choice. Indeed it is, as it is the most nutritious drink containing all what a newborn needs. Apart from containing carbohydrates, fatty acids, lactoferrin, vitamins, immunological mediators, and others, it also contains antimicrobial proteins and bacteria itself. Yes, babies get microbes through their mother’s milk. Healthy mothers with a balanced gut microbiota will transfer the friendly bacteria that colonize the neonatal intestines through their milk. So how do bacteria end up in maternal milk? It has been indicated that maternal gut bacteria travel to the mammary glands through the lymphatic and circular pathways, forming together with a mammary skin microbiota a main bacterial composition provided to a baby while breastfeeding.
Formula-fed infants, in comparison to breast-fed infants, receive a different combination of nutrients, carbohydrates and bacteria, leading to a different bacterial gut colonization and a different pattern of immunity development. As a result, healthy breast-fed babies have more intestinal colonization with Bifidobacteria than healthy formula-fed babies. The latter have broader bacterial scope, including Bifidobacteria, Bacteroidetes, Clostridia, Enterobacteria and Streptococci.
Premies and their gut microbes
Babies born pre-term are challenged in many ways when facing the new world and acquiring their bacterial partners. They are often born with underdeveloped organs and immune systems, and with a low birth weight. They are often being exposed to a number of medications to increase their survival chances and to help their organs to mature. It sets a tougher starting point for them in comparison to full-term born infants in general, and in terms of their microbiome maturation. I was born prematurely at about 36 weeks gestational age together with my twin sister, so it’s very interesting for me to know what happens when premies meet the microbes. It has been reported that pre-term babies have lower microbial gut diversity than full term babies, Bifidobacterium is less abundant, and there is an increased number of pathogenic strains. Bifidobacterium species are believed to be key players in the development of a healthy gut microbiota. The unfavorable combination of factors makes premies fragile and more vulnerable to all sorts of conditions such as life-threatening infections or serious diseases including necrotizing enterocolitis. The preterm gut microbiome reaches its adult-like pattern later than in the full term infants. Thankfully, the advances in medicine nowadays increase pre-term infants’ survival chances, while helping them to have normal lives in the future.
The infantile delicate gut microbiome, even in healthy full-term infants, is constantly exposed to many influences such as diet, environment, medications, and pathogens. These may in turn lead to changes in microbial composition, leading to imbalance – dysbiosis, and even have a profound effect on short- and long-term health. Hopefully, growing knowledge in the field will help us make better choices around the birth and developing healthy infantile microbiota for our children.