>You have a bit of a misunderstanding here - a baby does not have a microbiome in the womb - it is a sterile environment
no. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4350424/
"The first, and most important, contribution to the genesis of the microbiome is vertical transmission of maternal microbiota. Colonization of mucosa in the digestive, respiratory, urogenital tracts, as well as the skin begins at, or perhaps even before, the time of birth when a newborn is exposed to a mother’s microbiota. It was previously thought that the in utero environment was largely sterile and that a fetus was not colonized with bacteria until the time of birth. Recent studies suggest the presence of a microbiome within the placenta as well as fetal meconium, suggesting that the colonization process begins well before delivery. "
And my point is that the "most important, contribution to the genesis of the microbiome" probably gets hit with the antibiotics given for C-section.