You might already know that we cannot survive without the trillions of microbes that live in and on our bodies, influencing everything from gut and skin health to our immune systems. But did you ever wonder, how we got these microbes in the first place? To find out, we have to go back to the beginning…
Pregnancy and the Vaginal Microbiome
Everything starts with our mothers. Research shows the critical role of the vaginal microbiome in the initial colonization of the infant’s microbiome. While microbial diversity in the vagina is already lower than in other microbiomes, a normal pregnancy is characterized by a greater degree of stability of the vaginal bacterial community than observed in non-pregnant women.  Specific characteristics of the vaginal microbiome, including the L. crispatus dominant state, can change during pregnancy and can so increase the risk of adverse pregnancy outcomes, like preterm births. 
(I wrote this article for MyMicrobiome.info and publish it here with kind permission of MyMicrobiome.)
Vaginal Birth vs. C-Section
While passing through the birth canal, the baby is exposed to the mother’s vaginal and intestinal flora, which get on its skin and in its mouth, thereby, seeding their oral, gut and skin microbiome.  With Caesarian sections, however, a baby’s first microbial contact is the hospital environment and the mother’s skin.
We therefore see different microbial compositions in newborns, based on the mode of delivery. C-sections, which account for more than 1 in 5 births (21%) worldwide , are associated with adverse health outcomes like increased risk for obesity, inflammatory bowel disease (IBD) and other immune and metabolic disorders. 
As the importance of the vaginal microbiome for the offspring’s health is being recognized, vaginal seeding is becoming more commonly known. In 2021 the first longitudinal study showed, how swabbing the newborn with the mother’s vaginal fluids right after birth, naturalizes the microbiota of C-section-born infants long-term. 
Breastfeeding and beyond
The colonization of the microbiome continues with nursing, where we also see different microbial compositions in breast- vs. formula-fed babies. [7, 5] The exposure to microbes is especially high in children under 3, as they crawl on the floor and put everything in their mouths to explore the world. After 3 years, the microbiota becomes adult-like. 
Bottom line, if mothers’ microbiomes are not healthy, it can have long-term adverse health consequences for future generations.
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