We were watching the start of Inside The Human Body the other night at MIL's, DD2 was asleep on the boob, DD1 was on MIL's knee and DP's 16yr old cousin J was there.
J and i were discussing how ti was nice to see a water birth and having a laugh about DD1's birth and medical intervention (she's a very intelligent 16yr old) when the baby was 'crowning'.
DD1 looked at the screen and said whats that, we all said It's a baby.

DD1 turns and says "is her bum falling out"

I know she's a little too young to understand but i explained no a baby comes out of the ladies ginny, so she watched the baby be bought to the surface and cry and i think she 'got' that it was a baby but man i nearly pee'd myself.
She was sooo serious when she said it... god i love kids.