Where do babies come from?

so, today we visited with my sister-in-law whose baby is due in 3 weeks. i told my 3-yr-old josh that he'd have a new cousin to play with very soon.
he said where?
he's in her belly now, but will come out soon.
he walks around her studying her very large belly and says did you eat it???
ahhh, what fun! now, how to scrap that one???