I know they get their oxygen from the mother via the umbilical cord of course... but they grow in what is essentially a sack of liquid- where does the air come from that is in their lungs while in the womb? 
Do they have air in their lungs in the womb? I mean when they get born after a slap on the ass they basically start breathing air- I know they remove some sludge from the nose or something to open up the airway but their lungs must have had air in them- it's not like you have to hang them upside down to drain the fluid from their lungs...
So I never thought about it before- and of course it isn't just for human babies- all animal babies with lungs seem to be born with air in them- for larger animals like elephants and whales that has to be a substantial amount of air.

Do they have air in their lungs in the womb? I mean when they get born after a slap on the ass they basically start breathing air- I know they remove some sludge from the nose or something to open up the airway but their lungs must have had air in them- it's not like you have to hang them upside down to drain the fluid from their lungs...
So I never thought about it before- and of course it isn't just for human babies- all animal babies with lungs seem to be born with air in them- for larger animals like elephants and whales that has to be a substantial amount of air.
