Amniotic Fluid: What It Is & Why It’s Important

Your baby sleeps and swims in it. They even play and, yes, pee in it. Amniotic fluid is essential to a healthy pregnancy and does so much more than cushion your kid while they’re in your belly for nine months. If you’ve ever wondered what amniotic fluid is, and why it’s so important during pregnancy, read on, because it’s so much more than your fetus’ own private (and perfectly temperate) pool.

What is amniotic fluid?

“Amniotic fluid is the fluid that surrounds your baby inside your uterus,” Dr. Greg J. Marchand, an OB-GYN and accredited master surgeon tells Romper. “This fluid has a lot of purposes and protects your baby’s skin for the nine months it is growing.”

But, what is amniotic fluid actually made from? “It is mostly made of water from the pregnant person’s body,” adds Dr. Lauren Demosthenes, an OB-GYN. “After 20 weeks, it is mostly made up of the baby’s urine and lung secretions.” Yes, that’s right — your baby is swimming, splashing, and doing somersaults in their own pee. But don’t worry, because amniotic fluid, for the most part, is sterile, according to a PubMed study.

Why is amniotic fluid important?

Serving many purposes, amniotic fluid is the unsung hero of pregnancy. First and foremost, it keeps your baby comfy and cozy in the womb. “The fluid serves as a cushion for the baby and allows the baby to move freely in the uterus,” Demosthenes says. Amniotic fluid helps protect Baby from any potential trauma or impact. “It also allows the umbilical cord to be free and reduces compression,” Demosthenes adds.

Amniotic fluid also supports the development of the fetus in more direct ways. “Many aspects of fetal development depend on the amniotic fluid, most importantly the lungs,” Marchand says. “Without the fluid, the lungs will not develop properly.” Amniotic fluid levels can also serve as an indicator of how well the placenta is functioning, Marchand adds, since a failing placenta will not to bring enough blood to the baby, which causes amniotic fluid levels to drop.

Amniotic fluid can also filter infections and protect the baby, thanks to its antibacterial properties, researchers found. It offers vital nutrients for the baby as well, such as proteins, electrolytes, immunoglobulins, and vitamins from the pregnant parent.

What does amniotic fluid look like?

Is it clear? Does it have a color? If so, what color is amniotic fluid? “It is usually a thin fluid similar to water with a yellow tinge,” Marchand says. “For this reason, it can be difficult to tell from urine in some cases, and this can make it difficult for a mother to tell if her water is broken.”

Even though amniotic fluid is generally clear or very light yellow, there are times when the color can change — and that’s when there might be a cause for concern. “Amniotic fluid can be bloody red if there has been some bleeding from the placenta, such as with an abruption,” Marchand says.

Is there such a thing as green amniotic fluid?

Green amniotic fluid is common and has one culprit: meconium (otherwise known as Baby’s first BM). “Sometimes, the amniotic fluid will be green-tinged when the baby has a bowel movement inside the womb,” Demosthenes explains. “This typically happens later in pregnancy and is discovered when the water breaks. Occasionally a baby will inhale some of the meconium and will end up needing some extra help breathing, such as oxygen, until their lungs can recover from the exposure,” Marchand adds. This sounds like a big deal, and rarely it can be, but try not to freak out. It’s very common and usually not a big deal. “Although it is something we pay close attention to, usually it is not a serious problem and can be suctioned away from the baby’s mouth prior to breathing.”

Is amniotic fluid sticky?

Since amniotic fluid is responsible for housing your baby, filtering out any unwanted agents, and is composed of urine, you might think that it has a texture. But it typically doesn’t. “It’s mostly watery, but if it contains meconium, it could be sticky,” Marchand says. “I suppose if you let it dry on you it would be somewhat sticky, but most people wash it off if they get splashed!”

How is amniotic fluid measured?

Your amniotic fluid levels will go up and down as your pregnancy progresses, and as the fetus grows. Still, it’s important that safe levels of amniotic fluid are always present so that your baby stays healthy, so it is something that your doctor or health care provider will pay attention to. “It is not necessary to measure the amount of amniotic fluid if the growth of the baby is normal through the pregnancy,” Demosthenes explains. “If the growth seems below or above what is expected (measured by fundal height during the pregnancy), then an ultrasound may be ordered to look at the baby’s growth.” An ultrasound can be utilized to measure your baby’s size as well as the amniotic fluid, too.

And if they do need to measure it, exactly how is amniotic fluid measured? “The most commonly used system of measuring is called the Amniotic Fluid Index, or AFI,” Marchand continues. “It is a system where you measure the largest single up and down pocket of fluid in each of the four quadrants of the abdomen, while holding the ultrasound probe straight up and down.” By adding the numbers together, your health care professional will get a number of centimeters that will show them if your amniotic fluid levels are safe.

What is the normal range of amniotic fluid?

“Although we don’t correlate the centimeters in the AFI directly with ounces of fluid in the abdomen, we consider a normal range for the amniotic fluid index to be 5 to 25 cm,” he says. “This correlates with about a quart of fluid at term.”

If your health care provider finds that you do have too much amniotic fluid, it could be due to polyhydramnios. “Polyhydramnios is a condition with too much fluid, and this may be from gastrointestinal malformations of the baby, neurologic problems with the baby, or obstruction of the baby’s esophagus,” Demosthenes explains. “Also, uncontrolled diabetes in the mother can cause too much urine production in the baby leading to too much fluid.”

What happens if amniotic fluid is low?

Too much amniotic fluid can be a cause for concern, and on the flip side, if amniotic fluid is low, your doctor will want to know as well. But what causes low amniotic fluid? “The most common cause is the water being broken, but other causes, including a placenta failing, could be the culprit,” Marchand says. “Therefore, if these pregnancies are more than 23 weeks, then these will be pregnancies we watch very closely, usually keeping the mother in the hospital until birth.”

“Decreased amniotic fluid is known as oligohydramnios,” Demosthenes says. “This may be from the baby’s kidneys not working properly or leaking of fluid.” Unfortunately, leaking amniotic fluid cannot be replaced, and so if your health care provider suspects that you are leaking fluid, they will want to figure out why as quickly as they can. Your health care provider can do a speculum exam to confirm if you are indeed leaking amniotic fluid.

What does leaking amniotic fluid look like?

Since it’s often colorless and odorless, it can be hard to tell if you’re leaking amniotic fluid or if you’re just experiencing normal pregnancy-related discharge. “I get calls every week about my patients who think their water could be broken,” Marchand says. “While usually there is a gush, there isn’t always, so I always tell my patients that are more than 23 weeks that if you think your water could be broken it is best to go in to check.” Your doctor can perform an exam or possibly order an ultrasound to see if your amniotic fluid levels are in the normal range, or just provide reassurance that your pregnancy is healthy and progressing normally.

Apart from keeping your fetus feeling warm and snug in the womb, amniotic fluid keeps your baby safe by staving off infection, it boosts their digestive system, and even helps your baby’s bones and muscles develop, thanks to all those in-utero backflips. If you’re ever concerned that you might be leaking amniotic fluid, it’s a good idea to speak with your health care provider right away.

Studies referenced:

Fitzsimmons, E., Bajaj, T. (2022) Embryology, Amniotic Fluid. StatPearls, https://www.ncbi.nlm.nih.gov/books/NBK541089/

Lim, E., Rodriguez, C., Holtz, L. (2018) Amniotic fluid from healthy term pregnancies does not harbor a detectable microbial community. Microbiome, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5946436/

Hwang, D., Mahdy, H. (2022) Polyhydramnios. StatPearls, https://pubmed.ncbi.nlm.nih.gov/32965811/

Experts:

Dr. Greg J. Marchand, M.D., FACS, FACOG, FICS, an OB-GYN and accredited master surgeon

Dr. Lauren Demosthenes, M.D., an OB-GYN and senior medical director with Babyscripts