http://mobile.news.com.au/lifestyle/parenting/maxxzandra-ford-didnt-know-she-was-pregnant-then-had-14-pound-baby/story-fnet08xa-1227212642749 Ouch
I know! It's not like one of those stories about a teenager who had a bad stomachache one day, and to her surprise, gave birth sitting on the toilet.
I can understand if you're on some sort of birth control and don't really get periods you may not notice for a few months but by the 6th month there should be some tell-tale signs there.
No, they don't let you tear. They cut you and stitch you back up. Bowel movements are terrible for a while after...and sitting.