A product of fetal metabolism, amniotic fluid serves several purposes: It helps exchange substances between mom and baby, it acts as a physical barrier that protects the fetus (a sort of cushioning to protect against trauma, such as a car accident), and it also works as part of a baby's immune system as it contains immune chemicals that fight viruses and bacteria. (Another cool fact: It also coats both sides of the tympanic membrane in the baby's ear, which allows sound to pass through from the outer ear to the inner one.)
Babies also need amniotic fluid for lung development. A newborn baby's lungs are like crumpled Saran Wrap. When a fetus inhales amniotic fluid, it stimulates the production of surfactant in the lung tissue, which lubricates the airways and allows the lungs to mature.
Find out more about this book:YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy