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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.

Information

While in the womb, the baby floats in the amniotic fluid. The amount of amniotic fluid is greatest at about 34 weeks (gestation) into the pregnancy, 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
  • 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.

References

Burton GJ, Sibley CP, Jauniaux ERM. Placental anatomy and physiology. In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 1.

Gilbert WM. Amniotic fluid disorders. In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 35.

Ross MG, Beall MH. Amniotic fluid dynamics. In: Creasy RK, Resnick R, Iams JD, Lockwood CJ, Moore TR, Greene MF, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 7th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 3.

    • Amniocentesis

      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

      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

      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

      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 amniocentsis to check for chromosomal defects or other abnormalities.

      Amniotic fluid

      illustration

      • Amniocentesis

        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

        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

        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

        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 amniocentsis to check for chromosomal defects or other abnormalities.

        Amniotic fluid

        illustration

      Tests for Amniotic fluid

       

      Review Date: 12/10/2016

      Reviewed By: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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