[U]sing a delicate sensor-belt wrapped around the chests of full-term newborns moments after their delivery, a team of researchers from Australia, Germany, Switzerland, and Canada have recorded the changes in lung volume that occur in a baby’s first minutes outside the womb.
Putting it simply, while the babies are snug inside the uterus, they’re busy exercising their lungs: Though crammed full of a liquid secreted by the lung’s lining, they still move in a semblance of breathing to give the brain and muscles plenty of practice.
This training regime drops immediately before birth. The big squeeze that comes with being pushed through the vaginal canal forces out some of the liquid, while also providing a generous dose of adrenaline that tells the lungs to soak up as much of that fluid as they can.
That still leaves a fair bit of residue sloshing about, especially if delivery came via caesarean. Much of it is pushed back through the tissues with the first rush of air, with a soapy material called a surfactant helping the tiny air sacs shed their coating of fluid more easily and expand as wide as possible.
It’s little wonder that our first moments swanning about in the open air come with a gurgling cry.