Throughout the animal kingdom, mothers transfer microbes to their young while giving birth. For instance, tadpoles acquire skin bacteria from their mothers, and chicken eggs acquire microbes from a specialised pouch near the hen’s rectum.
While you were in the womb, you were as close to microbe-free as you can get. There were very few microbes within the membrane that sealed you from the outside world. The moment your mother’s water broke, you suddenly came into contact with millions of microbes. That first contact with microbes is really critical.
The first microbes to make contact with your sterile body colonise and penetrate deep into the skin. The first contact with microbes influences your skin microbiome all the way into adulthood.
Five days before you were born (if you were born naturally), your mother’s body started to make changes to the microbiome in the birth canal. The vaginal cells secreted peptides that shifted the balance in favour of Lactobacillus bacteria. As you left the womb, your body was seeded with the microbes that your skin needed.
These first microbial colonists would colonise deep into your skin and interact with your immune system to let it know that they were there to help.
During birth the skin is colonised by hundreds of microbial species. Mothers seed their child’s skin with a mix of protective microbes that will form long-lasting bonds with their skin cells and educate their immune systems to respond appropriately to threats. A Caesarean section short-circuits this seeding by denying exposure to vital microbes present in the birth canal. The figure below illustrates the difference between the average skin microbiome of a vaginally delivered baby and that of a baby born by Caesarean section. The C-section child would not have come into contact with vaginal microbes. The skin microbiomes of these two children are completely different. It is interesting to look at the percentage of Lactobacillus (indicated in red) in each child.
Good news is that the microbiome does normalise over time, however Lactobacillus population is still about 10 times larger in naturally delivered adults.
The physiological stress of giving birth caused your mother’s body to transport a huge diversity of microbes to her breast milk, so that the first drink of colostrum would seed your intestine with the probiotic microbes that would then go on to colonise your gut and establishes links with your immune system. The colostrum also contains prebiotics that are nutrients for these probiotic microbes.
Your mother would continue to give you the probiotic microbes that you needed via breast milk, and it has been shown that the microbial community in breast milk changes substantially over the first six months of breastfeeding.
This early contact crafted a healthy relationship between the microbiome and immune system. Breakdowns in this early interaction have been linked to many auto-immune diseases like diabetes.
So, your mother went to great lengths to shape your microbiome, because it would shape the person that you would become.