This has been known for quite a while, basically passing through the non sterile vaginal canal vs the sterile (or close to it) abdominal wall yields differences. This has lead to some questionable practices such as "vaginal seeding" whereby new moms will swab their vagina and then seed their babies shortly after birth (usually through placing the gauze in babies mouth or around their face). This comes up not infrequently at the hospital I work at. I think much of it stems from Facebook rather than actual discussions with their OB.