Amniotic Fluid

Overview

What is amniotic fluid?

Amniotic fluid is a water-like substance surrounding the fetus in your uterus. The fetus grows inside an amniotic sac filled with amniotic fluid during pregnancy. The amniotic sac forms around 12 days after you become pregnant. When your water breaks (a sign of labor), your amniotic sac breaks and amniotic fluid leaks from your vagina.

Amniotic fluid is more than just a liquid the fetus floats in. Amniotic fluid contains nutrients, hormones, antibodies and other fluids to help keep the fetus healthy and protected. Amniotic fluid is constantly circulating because the fetus swallows it, then urinates it out. Having too little or too much amniotic fluid could cause problems for a pregnant person or the fetus.

Function

What does amniotic fluid do?

Amniotic fluid has an important job in the uterus. It helps with fetal growth and development. Among other things, it:

  • Protects the fetus from infection.
  • Cushions the fetus's movements and helps it move.
  • Helps the fetus's muscles and bones develop.
  • Prevents the umbilical cord from getting compressed.
  • Helps the fetus's digestive and respiratory systems develop.
  • Regulates fetal body temperature.
  • Protects it from your movements (like a fall or sudden blow).

Why is amniotic fluid important?

Amniotic fluid is necessary for a healthy pregnancy and helps prepare the fetus baby for the outside world. It acts as a cushion to protect them from your movements. This same cushion allows them to move freely and develops their muscles and bones. The fluid prevents the umbilical cord from compressing. The umbilical cord transports oxygen and nutrients from you to the fetus and could become squished without amniotic fluid. Amniotic fluid contains antibodies to help strengthen the fetal immune system. The fetus practices breathing and swallows amniotic fluid to help develop its lungs and digestive system.

How is amniotic fluid measured?

Healthcare providers measure amniotic fluid using ultrasound. They measure pockets of amniotic fluid in specific areas of the amniotic sac, then calculate the total volume of fluid.

Anatomy

What color is amniotic fluid?

Amniotic fluid is mostly clear but can be a pale yellow like the color of straw. Amniotic fluid that's tinted brown or green means the fetus has passed meconium (their first poop) in your uterus.

Meconium in amniotic fluid can cause complications if the fetus breathes it in. In severe cases, the fetus may develop meconium aspiration syndrome and need immediate treatment after birth.

What does amniotic fluid smell like?

Amniotic fluid should be odorless. Contact your healthcare provider if you notice a foul smell as it could be meconium-stained or mean there is an infection.

Is amniotic fluid sticky?

No, amniotic fluid isn't sticky. If you feel sticky vaginal discharge, it might be your mucus plug.

What creates amniotic fluid?

Amniotic fluid is mostly water for the first half of pregnancy. The fetus's pee makes up most of the amniotic fluid after about 20 weeks of pregnancy. This is because, like adults, the fetus will swallow liquid and pee it out.

How many liters of amniotic fluid is normal?

It depends on how far you are in your pregnancy. Your amniotic fluid levels peak at 34 to 36 weeks and then slowly decrease as you reach your due date (40 weeks). At its peak, there is a little less than 1 liter of fluid in the amniotic sac.

Conditions and Disorders

What are signs of leaking amniotic fluid?

Some pregnant people leak amniotic fluid during pregnancy. Amniotic fluid is clear, thin and odorless. It can have a hint of color (brown, green or yellow are most common). It's common for pregnant people to leak urine, so some people have difficulty distinguishing amniotic fluid from pee. Inspecting your underwear for smells or color can help you determine what it is. Urine has a unique smell and may be easier to control than amniotic fluid.

If you feel a strong gush of fluid from your vagina, it could be your water breaking. But there is an increase in vaginal secretions late in pregnancy, so it can be hard to tell the difference. Contact your healthcare provider if you believe your water has broken or if you're confused about what is leaking from your vagina.

What happens when you have low amniotic fluid?

Low amniotic fluid is called oligohydramnios. Low amniotic fluid affects about 4% of pregnant people. Several factors can contribute to low amniotic fluid. Some of them are:

  • Congenital conditions that affect your baby's kidneys or urinary tract.
  • Going more than two weeks past your due date.
  • Gestational diabetes.
  • Growth-restricted babies.
  • Early rupture of membranes.
  • Problems with the placenta.
  • Twins that share the same placenta.

What are the complications of low amniotic fluid?

Low amniotic fluid in the first six months of pregnancy is generally more dangerous. These complications could include miscarriage, physical deformities of the developing baby including lungs that don’t develop properly or premature birth.

If you're diagnosed with oligohydramnios in the last trimester (weeks 28 to 40) of pregnancy, complications could include:

  • Umbilical cord compression.
  • Fetal growth restriction.
  • Respiratory issues.
  • Increase risk of cesarean delivery.

How is low amniotic fluid treated?

It depends on how far along you are in your pregnancy. If you're close to full term (37 weeks of pregnancy), your healthcare provider may schedule an induction or monitor you more closely until delivery.

What happens if you have too much amniotic fluid?

Too much amniotic fluid is called polyhydramnios. It's a rare condition that causes symptoms like swollen feet, breathlessness or constipation.

Moderate to severe polyhydramnios could be caused by:

  • A congenital condition affecting the fetus's ability to swallow.
  • Gestational diabetes.
  • Carrying identical twins with transfusion syndrome (TTTS).
  • Problems with the fetus's stomach.
  • Issues with the placenta.

What are the complications of too much amniotic fluid?

If you have too much amniotic fluid in your uterus, it can put pressure on neighboring organs. This can cause pregnancy complications, especially if the condition shows itself early into the pregnancy. Other complications include:

How do doctors treat high amniotic fluid?

Polyhydramnios is usually not treated unless it's necessary. Your healthcare provider may schedule additional appointments to check on the size of the fetus. In severe cases, medication can control fetal urine production while in your uterus. Your provider may also recommend early induction, bed rest, or draining a small amount of amniotic fluid.

Care

Can drinking water increase amniotic fluid?

No one is entirely sure if drinking more water can increase amniotic fluid. Some healthcare providers will recommend a pregnant person increase their water intake if their fluid is low. There's no harm in drinking more water during pregnancy but talk to your provider first to see what they recommend.

Can a baby live without amniotic fluid?

No. A fetus needs some amniotic fluid in the uterus to survive. However, the exact amount of amniotic fluid it needs depends on its gestational age and other factors.

Can a baby drink amniotic fluid?

Yes, a fetus drinks amniotic fluid in the uterus. This helps them practice swallowing and develops their digestive system.

Does a baby breathe in amniotic fluid?

The fetus baby practices breath-like movements in amniotic fluid in your uterus. This helps with fetal lung development and teaches it how to breathe outside the uterus. Fetuses begin practicing breathing amniotic fluid in the first trimester.

A note from Cleveland Clinic

Amniotic fluid helps a fetus grow and protects it from injury and infection. Fetuses swallow and practice breathing amniotic fluid, then pee it out. Some pregnant people have too much or too little amniotic fluid. Your healthcare provider may monitor you more closely or perform additional ultrasounds if this happens to you. If you're concerned about your pregnancy or experience fluid leaking from your vagina, don't hesitate to talk to your provider.

Last reviewed by a Cleveland Clinic medical professional on 06/18/2022.

References

  • American Pregnancy Associations. Low Amniotic Fluid Levels: Oligohydramnios. (https://americanpregnancy.org/healthy-pregnancy/pregnancy-complications/oligohydramnios/) Accessed 6/18/2022.
  • American Pregnancy Association. Polyhydramnios: High Amniotic Fluid During Pregnancy. (https://americanpregnancy.org/healthy-pregnancy/pregnancy-complications/polyhydramnios-high-amniotic-fluid/) Accessed 6/18/2022.
  • Lord M, Marino S, Kole M. Amniotic Fluid Index. (https://www.ncbi.nlm.nih.gov/books/NBK441881/) [Updated 2021 Jan 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Accessed 6/18/2022.
  • March of Dimes. Amniotic fluid. (https://www.marchofdimes.org/pregnancy/amniotic-fluid.aspx) Polyhydramnios. (https://www.marchofdimes.org/complications/polyhydramnios.aspx) Accessed 6/18/2022.
  • Merck Manuals. Problems With Amniotic Fluid. (https://www.merckmanuals.com/home/women-s-health-issues/complications-of-pregnancy/problems-with-amniotic-fluid?query=oligohydramnios) Accessed 6/18/2022.

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