according to Sadie on Knocked up:
Sadie: Where do babies come from?
Debbie: Where do you think they come from?
Sadie: Well. I think a stork, he umm, he drops it down and then, and then, a hole goes in your body and there's blood everywhere, coming out of your head and then you push your belly button and then your butt falls off and then you hold your butt and you have to dig and you find the little baby.
Debbie: That's exactly right.