Amniotic fluid

Amniotic fluid is a clear, slightly yellowish liquid that surrounds the unborn baby (fetus) during pregnancy. It is contained in the amniotic sac.

While in the womb, the baby floats in the amniotic fluid. The amount of amniotic fluid is greatest at about 34 weeks into the pregnancy (34 weeks gestation), when it averages 800 mL. About 600 mL of amniotic fluid surrounds the baby at full term (40 weeks gestation).

The amniotic fluid constantly moves (circulates) as the baby swallows and "inhales" the fluid, and then releases it.

The amniotic fluid helps:

The developing baby to move in the womb, which allows for proper bone growth
The lungs to develop properly
Prevent pressure on the umbilical cord
Keep a constant temperature around the baby, protecting from heat loss
Protect the baby from outside injury by cushioning sudden blows or movements

Too much amniotic fluid is called polyhydramnios. This condition can occur with multiple pregnancies (twins or triplets), congenital anomalies (problems that exist when the baby is born), or gestational diabetes.

Too little amniotic fluid is known as oligohydramnios. This condition may occur with late pregnancies, ruptured membranes, placental dysfunction, or fetal abnormalities.

Abnormal amounts of amniotic fluid may cause the health care provider to watch the pregnancy more carefully. Removing a sample of the fluid through amniocentesis can provide information about the sex, health, and development of the fetus.

Open References

References

Burton GJ, Sibley CP, Jauniaux ERM. Placental anatomy and physiology. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 1.

Gilbert WM. Amniotic fluid disorders. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 28.

Ross MG, Beall MH. Amniotic fluid dynamics. In: Lockwood CJ, Copel JA, Dugoff L, et al, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 4.

Amniocentesis - illustration
Amniocentesis is used to determine the health of an unborn baby. Amniotic fluid contains cells that are normally shed from the fetus. Samples of these cells are obtained by withdrawing some amniotic fluid. The chromosome analysis of these cells can be performed to determine abnormalities. In addition, the cells may be cultured and analyzed for enzymes, or for other materials that may indicate genetically transmitted diseases. Other studies can be done directly on the amniotic fluid including measurement of alpha-fetoprotein.
Amniocentesis
illustration
Amniotic fluid - illustration
Amniotic fluid not only protects the fetus from injury and temperature changes, it also is circulated by the fetus every 3 hours.
Amniotic fluid
illustration
Polyhydramnios - illustration
Polyhydramnios may occur when a fetus cannot swallow a normal amount of amniotic fluid due to a gastrointestinal, neurological, or other problem.
Polyhydramnios
illustration
Amniotic fluid - illustration
Amniotic fluid surrounds the growing fetus in the womb and protects the fetus from injury and temperature changes. It also allows for freedom of fetal movement and permits musculoskeletal development. The amniotic fluid can be withdrawn in a procedure called amniocentesis to check for chromosomal defects or other abnormalities.
Amniotic fluid
illustration

Amniocentesis - illustration
Amniocentesis is used to determine the health of an unborn baby. Amniotic fluid contains cells that are normally shed from the fetus. Samples of these cells are obtained by withdrawing some amniotic fluid. The chromosome analysis of these cells can be performed to determine abnormalities. In addition, the cells may be cultured and analyzed for enzymes, or for other materials that may indicate genetically transmitted diseases. Other studies can be done directly on the amniotic fluid including measurement of alpha-fetoprotein.
Amniocentesis
illustration
Amniotic fluid - illustration
Amniotic fluid not only protects the fetus from injury and temperature changes, it also is circulated by the fetus every 3 hours.
Amniotic fluid
illustration
Polyhydramnios - illustration
Polyhydramnios may occur when a fetus cannot swallow a normal amount of amniotic fluid due to a gastrointestinal, neurological, or other problem.
Polyhydramnios
illustration
Amniotic fluid - illustration
Amniotic fluid surrounds the growing fetus in the womb and protects the fetus from injury and temperature changes. It also allows for freedom of fetal movement and permits musculoskeletal development. The amniotic fluid can be withdrawn in a procedure called amniocentesis to check for chromosomal defects or other abnormalities.
Amniotic fluid
illustration

A Closer Look

Talking to your MD

Self Care

Tests for Amniotic fluid

Amniocentesis

Review Date: 11/10/2022

Reviewed By: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Health Library

Amniotic fluid

Gestation

Polyhydramnios

Gestational diabetes

Placental dysfunction