Skip to main content

Understanding amniotic fluid and its function

Amniotic fluid is a fluid that protects and supports when the fetus grows in the uterus. The amniotic fluid is produced after the amniotic sac is formed or about 12 days after fertilization. The function of amniotic water is vital for the fetus. Among them to protect the fetus from impact, help the development of the legs, muscles, lungs, and fetal digestive system. Amniotic fluid is located in the amniotic sac. The color of the amniotic water is clear and slightly yellowish, but looks clear and has no odor. In this amniotic fluid the fetus floats, breathes, and moves. The fetus also swallows the amniotic fluid, expels it as urine, then swallows it again. This aims to maintain the stability of the amniotic water volume. Too much or too little amniotic fluid can harm pregnancy.

Amniotic Water Composition and Volume

Amniotic water is composed of nutrients, hormones, and immune-forming cells that are useful for supporting fetal development. At 20 weeks, the composition of the amniotic fluid is dominated by fetal urine. Amniotic fluid volume will continue to increase during pregnancy. However, when the womb reaches 38 weeks of age, the volume decreases to prepare for birth. The following estimates of normal amniotic water volume:
  • 60 milliliters (mL) at 12 weeks of gestation.
  • 175 milliliters (mL) at 16 weeks of pregnancy.
  • 400-1,200 milliliters (mL) between 34-38 weeks of gestation.
The volume of amniotic fluid can be too much (polyhydramnios) or too little (oligohydramnios). Both of these conditions are dangerous for the development and safety of the fetus. Therefore, consult an obstetrician to find out the normal volume of amniotic water. The doctor will do a pregnancy ultrasound examination to assess whether the amniotic water volume is appropriate for the age of the womb.

Amniotic Water Function

Important functions of amniotic fluid include:
  • Give space to the fetus

  • Amniotic fluid allows the fetus to have room to move. A fetus that moves frequently indicates that it is getting enough nutrients and oxygen.
  • Supports the development of muscles and bones

  • The movement of the fetus in the womb helps to form and increase the strength of muscles and bones of the Little One.
  • Maintain the ideal temperature

  • Amniotic sacs and water maintain ideal temperatures to keep the fetus comfortable. The temperature of the amniotic fluid is usually slightly higher than the body of the mother, which is around 37 degrees Celsius.
  • Detect genetic disorders

  • Under certain conditions, your doctor may recommend genetic testing through a sample of amniotic fluid in the mother's uterus. This examination is called amniocentesis. This can be done because the amniotic fluid contains flakes of fetal skin cells. Amniocentesis examination should be done before entering the second trimester of pregnancy.
  • Protect from impact

  • The amniotic fluid protects the fetus from shock, impact, or pressure on the mother's abdomen.
  • Help the development of the lungs

  • The fetus does not breathe like the way we breathe. The fetus relies on maternal breathing to receive oxygen. At 10-11 weeks' gestation, the fetus begins to breathe a little amniotic fluid. Although inhaling, its movements are more like swallowing. This activity helps the development of the lungs. By the age of 32 weeks of pregnancy, the fetus will begin to practice breathing movements which are a combination of swallowing and lung contractions.
  • Help the development of the digestive system

  • Swallowing the amniotic fluid plays an important role in the development of the fetal digestive system. Difficulty swallowing amniotic fluid can result in too much amniotic fluid volume, which leads to the risk of pregnancy complications.
  • Protect from infection

  • Amniotic fluid plays a role in protecting the fetus from infection by stopping the growth of certain types of bacteria.
The amniotic sac will generally break before birth. When your fetus is ready to be born, amniotic fluid will flow from the vagina. After that, you may experience firmer and more regular contractions. See your doctor immediately if premature rupture of membranes occurs, amniotic fluid is thick green and foul-smelling, or you have a fever just before delivery.