What is amniotic fluid?

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

No matter your favorite fluid of choice - water, tea, a venti pumpkin spice latte - it's time to appreciate another. The most important fluid moms need to know about is the one that acts a bit like an air bag for your developing baby: Amniotic fluid.

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.

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YOU: Having a Baby: The Owner's Manual to a Happy and Healthy Pregnancy

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Dr. Jeanne Morrison, PhD
Family Practitioner

Amniotic fluid consists mostly of water with small amounts of organic and inorganic substances such as albumin, urea, creatine, phospholipids, fructose, fat, leukocytes, epithelial cells, enzymes and hair.  The composition of amniotic fluid changes over the course of the pregnancy.  In early pregnancy, amniotic fluid has a composition similar to maternal plasma and in later pregnancy the amniotic fluid becomes hypotonic due to the presence of fetal urine.  

The amniotic fluid serves a number of functions for the developing embryo/fetus.  The amniotic fluid:

  • surrounds the developing fetus
  • helps to maintain a constant body temperature and
  • cushions the fetus from trauma by blunting and dispersing outside forces

In addition, the fluid-filled cavity provides an environment that allows free movement for muscular development.  The fluid also keeps the embryo from becoming entangled with the membranes and facilitates symmetrical growth of the fetus.  

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.