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How Fetuses Breathe

July 24, 2007

A listener asks: How do babies breathe inside the womb?


Breathing in the womb. I’m Bob Hirshon and this is Science Update.

The womb is filled with fluid, so listener Gillian of Gainesville, Florida, writes to ask how babies breathe in there. We turned to cardiovascular physiologist John Stallone of Texas A&M. He says fetuses actually don’t breathe at all, because their mother breathes for them.

JOHN STALLONE (Texas A&M University):
They receive their oxygen through the placenta, which is just the shared circulation between the mother and baby.

So when the mother breathes, oxygen enters into her bloodstream, and some of it crosses the placenta into the baby’s blood. It’s only at birth when the connection between mother and baby is cut that the lungs are forced into action. If you have a science question, call us at 1-800-why-isit. If we use it on the air, you’ll win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.