Where do babies come from?

Today Bridger came home from school and asked me, " how do you know where babies come out of?" I wasnt quite sure what to say in response and just said "because ive had 3 babies." He looked at me for a minute and said, so is it like a bird laying an egg? I tried not to laugh and told him yes, its something like that. He looked at me with a grossed out look and said, SICK! I couldnt help but laugh.