Your colon is sterile when you're born, which leaves it basically unprotected against the various horrors that will travel through it. The exposure to your mother's fecal matter the moment you're born is custom designed to take care of this glaring error. The way it does so is the stuff of horror movies, though.
The mom's poop bacteria creeps up the child's colon and infests it. Thus, your mum's colon bacteria is stuck with you for life, which in turn greatly contributes to the smell of your own crap and even farts. As disgusting as the idea that you and your mom are poop-mates may be, it's a shitload (sorry) better than the alternative. Babies that are born via C-section -- and have therefore not been exposed to shit, vaginal mucus and all the other wonders of a traditional childbirth -- have much worse immune systems (and presumably worse-smelling farts) precisely because they weren't subjected to mom-poop and therefore have to later develop their own colon bacteria from breast milk and whatnot.
Read more: http://www.cracked.com/article_19913...#ixzz2JiLPiQ3Q