Baby's First Breath

When a baby is inside its mother, its lungs are deflated. They’re essentially in a breathed-out half-collapsed state that’s supported by amniotic fluids. When the baby comes out, the sudden change of environment and temperature causes the body to begin its first inhalation. The lungs expand, blood flow to the lungs increases, and the fluid is absorbed. The first breath is raspy because the fluid is still there; but the lungs were never full of it, so the expanding space is filled with fresh air.

The sudden rush and overload on its senses, bright light stinging their eyes that were used to near-total darkness, the rush of sounds closing in and everything else associated with the birthing process totally tires the baby, so they sleep for nearly 24 hours afterward, misleading new parents to think they have got a really easy baby.