C-section babies are prone to certain ailments later in life:

"Giant study links C-sections with chronic disorders" -

http://sciencenordic.com/giant-study-links-c-sections-chroni...

My guess is that this is tied to the reduced exposure to the mothers' vaginal and anal microbiome that occurs during vaginal delivery but which is absent in C-section.

Much as childhood exposure to animals reduces autoimmune disorders in later life, natural birth also likely does the same.

"Study: Children who grow up on family farms and drink raw milk have fewer allergies, autoimmune disorders"

https://www.naturalnews.com/035802_raw_milk_farms_allergies....