What Is the Amniotic Fluid?

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Amniotic Fluid Important

For many, amniotic fluid is one of those things you hear about in pregnancy but you may not know much about. How often have you stopped to wonder, what is amniotic fluid, anyways? You know it’s important, but with everything else going on, it might have fallen to the bottom of the list of “things to learn in pregnancy.” Lucky for you, we’ve pulled together the basics for a quick read.

What is amniotic fluid?

Amniotic fluid is the liquid that surrounds the fetus in its sac within your uterus while it’s growing. Generally speaking, the amniotic fluid consists of water, hormones, and nutrients. At first, this fluid is made from your own body fluids. But as pregnancy moves along, the baby begins to contribute. Once her kidneys begin to work, her urine begins to make up the amniotic fluid. At around 20 weeks, the amniotic fluid is mostly urine. Some of the fluid also comes from the baby’s lungs.

Why is it important?

Amniotic fluid is necessary for normal fetal growth and development. The many functions include:

  • Protecting the baby
  • Keeping the umbilical cord from being compressed between baby and the uterus
  • Providing enough space for the baby to move around
  • Providing a healthy environment for growth and development
  • Keeping a safe and steady temperature
  • Helping to prevent infection1,2

Amniotic fluid can also provide information about the baby because it contains fetal cells. The fluid can be removed from the sac using a very thin needle and tested during pregnancy (called “amniocentesis”), usually between 15 and 20 weeks. This testing can detect genetic disorders, or birth defects caused by problems in the baby’s genes. Some examples include Down syndrome, cystic fibrosis, and sickle cell disease. There is a slight risk of miscarriage after amniocentesis.3

Is there a “right” amount of amniotic fluid?

While the baby is floating around in the amniotic fluid, she also swallows some of the fluid. The amount of amniotic fluid increases during pregnancy until about 34 to 36 weeks. In late pregnancy, she probably swallows more than she makes, so the amount of amniotic fluid decreases.

As you know, regular ultrasounds are important during pregnancy. One of the many things doctors are looking for on an ultrasound is the amount of amniotic fluid within the sac. When there is less amniotic fluid than what is expected, it’s called “oligohydramnios.” The cause for this depends on many things, including how far along the pregnancy is. Some causes include:

  • Maternal dehydration (mother’s body does not have enough water)
  • Problems with the placenta
  • Problems that cause decreased urine or impaired swallowing from the baby
  • Premature rupture of membranes

When there is too much amniotic fluid, it’s called “polyhydramnios.” Causes for this include gestational diabetes (condition of poor sugar control during pregnancy), multiple pregnancies, or health problems of the baby.4

In summary, amniotic fluid is critical for your baby’s growth and development. Healthy babies are born despite conditions related to the amount of fluid, but it’s definitely something to keep an eye on. This is one of the many reasons why it’s important to get regular check-ups during pregnancy and ultrasounds when recommended.

References:

  1. Physiology of amniotic fluid regulation.
  2. March of Dimes. Amniotic fluid.
  3. American Congress of Obstetricians and Gynecologists. Diagnostic Tests for Birth Defects.
  4. Medline Plus. Amniotic fluid.
Mandy Armitage
Dr. Mandy Armitage is a board-certified physician and writer. She is passionate about education, for patients and clinicians alike. In her free time, she enjoys spending time with her family, reading, traveling, and attending live music events.

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