Why doesn't the fetus drown when it inhales and exhales amniotic fluid?

Answer 1

A baby doesn't drown in the womb because until they are born they don't ever breathe air, they don't need it. The umbilical cord, attached to the baby by the placenta on the mother's side, passes nutrients and oxygen in and removes wastes back to the mother's system for elimination. She does the breathing and eating for the baby (and the elimination too!) Imagine the umbilical cord as a Scuba setup - the mother is both tanks, and the good air comes in through the hose from one tank, the bad air (usually expelled at the mouth on scuba gear) goes back to another tank. Except in this case, instead of attached to the face, this mask is on the stomach, a direct line into the baby.

The reason for this system appears to be many reasons:

- The baby is physically protected both by the flesh of the mother and a fluid sac which can deflect any soft impacts and a lot of hard impacts away from the baby.

- Being built in a fluid allows delicate structures, brain, lungs, eyes, to be built slowly and in complex patterns with a much lower chance of being broken if they are built in a fluid. Imagine these organs (and others) as a latticework of crystals - grown thick and complex in adults they can take a lot of beating and regrow, but in a baby the basic 'brickwork' is still very fragile. {This seems to be the reason that doctor's like for babies to be in the womb as long as possible, the complex, brittle growth needed is much easier on the baby in-vitro.}

- It's easier for the mother's body to pass needed chemicals in to the baby at the correct intervals. In a dry system, all of the fluids would have to pass the placenta and there could a limit on the rate of flow (only so many cars can go down the same street at the same time.)

- When it's time to come out, the baby needs to be flexible and have lots of lubrication (LOTS AND LOTS) to be expelled from the womb. Were the baby dry, or not very wet, imagine a Bowling ball covered in sandpaper trying to come out of you!