The role of amniotic fluid

<< View all animations

Inside a pregnant woman’s uterus is an amniotic sac, which contains amniotic fluid and the growing fetus.

The amniotic fluid is important for several reasons -- it helps keep the baby warm, and because his body parts are growing so fast, the fluid provides lubrication that keeps them from growing together. In some cases, fingers and toes can become webbed as a result of not enough amniotic fluid circulating in the uterus. Amniotic fluid also helps the baby's lungs develop.

The amniotic fluid also lets the baby move easily so he can exercise his muscles and strengthen his bones before he’s born.

In addition, it acts like a liquid shock absorber for the baby by distributing any force that may push on the mother’s uterus. Even sex won’t hurt the baby.

Amniotic fluid is 98% water and 2% salts and cells from the baby. Until the fetal kidneys started working during month four, amniotic fluid is made by the mother’s body. But after month 4, the little guy started to make his contribution to the amniotic fluid by urinating into it.

You heard right. It may not sound appealing to us, but the urine in the amniotic sac is completely harmless to the baby.

The baby swallows amniotic fluid, which then passes through his digestive system, into his kidneys, and back out again to the amniotic sac as urine. In this way, he can practice using his digestive and urinary systems before he’s even born. In fact, doctors can tell by the amount of amniotic fluid whether the baby has difficulty with his swallowing reflex.

By the time he’s born, he will consume up to 15 ounces of amniotic fluid a day.


Need an appointment? Request one online 24 hours/day, 7 days/week or call 800-789-PENN (7366) to speak to a referral counselor.


A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission ( URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics ( and subscribes to the principles of the Health on the Net Foundation (

©Copyright A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites.

Related Links
Request an Appointment Online or call
1-800-789-PENN (7366)




About UPHS   Contact Us   Site Map   Privacy Statement   Legal Disclaimer   Terms of Use

The University of Pennsylvania Health System, Philadelphia, PA 1-800-789-PENN © 2016, The Trustees of the University of Pennsylvania