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Amniotic Fluid Levels In Pregnancy

Medically Reviewed by Caitlin Goodwin, MSN, RN, CNM
Updated
What level of amniotic fluid is normal?

Are you confused by the talk of amniotic fluid levels during your pregnancy? Are you concerned that your levels aren’t as they should be?

Every time you get an ultrasound during pregnancy, the technician will evaluate your amniotic fluid levels. It’s a standard way to check on your baby’s health.

In this article, we’ll explain what to expect of your amniotic fluid levels and discuss what you can do if your levels are too low or high.


What is Amniotic Fluid?

Following conception, an amniotic sac forms around the developing embryo. The sac is transparent and tough, growing as your unborn baby does. The sac increasingly fills with fluid until around the second trimester, as the baby takes over its production (1).

This watery substance contains essential fetal proteins and is clear in color. Babies swallow this fluid while they practice “breathing” and excrete it again as urine.

However, our kidneys clean it, so it is not as disgusting as it seems.

Amniotic fluid contents are vital for a healthy developing baby, providing the ultimate protection from the outside world.

Amniotic Fluid Benefits

We know the surrounding fluid also acts as a cushion to protect your unborn baby. It also has many other functions, which is what makes it so important.

Here are just a few:

  • Water levels: Allows the baby ample space for movement.
  • Temperature: Maintains a constant temperature for creating a healthy baby.
  • Aids healthy growth: Enables correct bone, muscle, and organ development.
  • Nutrient exchange: Enables vital nutrients between you and your baby, including oxygen, via the umbilical cord. If fluid levels change, the umbilical cord’s health can be compromised.

Amniotic Fluid Volume Assessment

At some point in your pregnancy, you’ll likely have an ultrasound scan, along with other tests. Particularly during your second and third trimesters, your sonographer will take detailed measurements of the amniotic fluid surrounding your baby. They will do this repeatedly if your measurements are low or high or if you have a high-risk pregnancy.

These measurements are also done as part of a fetal biophysical profile to understand your baby’s health in the uterus. Other parts of the biophysical profile include your baby’s breathing, movements, and flexion. While you are just excited to see your baby waving at you from within, the sonographer will be taking down lots of information.

I’ll admit, I never really knew what my obstetrician was doing. At my first scan, all I wanted to know was if there was a heartbeat.

During your prenatal visits, you will have blood tests, bump measurements, and your health care provider will take your blood pressure. However, your amniotic fluid is only examined via a sonogram.

Sometimes, amniotic fluid levels don’t appear to be within normal limits on a scan. If the clinician has advised that your fluid levels don’t seem right, they will follow you more closely. If your doctor wants to deliver your baby early due to complications, they may perform a procedure called amniocentesis to assess fetal lung maturity.

What Happens During Amniocentesis?

Although your health care provider may recommend this test for different reasons, it is mainly used to detect fetal or genetic abnormalities in your baby.

A very thin needle is inserted into the amniotic sac through your abdomen to draw out some liquid. It is then sent to a laboratory for analysis, where any chromosomal defects can be picked up.

While amniocentesis is generally viewed as a safe test, it does have possible risks, including miscarriage (2). Although it can be difficult to determine how many miscarriages are the direct result of amniocentesis, it is believed to be anywhere from 1 in 200 to 1 in 400.

What Will an Ultrasound Scan Detect?

In pregnancy, an ultrasound scan is sensitive enough to detect abnormally high or low amniotic fluid levels. It does this by emitting sound waves into the uterus through the stomach. These sound waves return a digital screen image (3).

If your obstetrician orders a sonogram to measure fluid around the baby, they will use clinical charts. This helps determine what they call the amniotic fluid index (AFI).

They do this by quartering the uterus (not literally!) and using the probe to measure the deepest pools of water. The measurements are taken in centimeters.

The results will be referenced in comparison to the clinician’s AFI chart. Your results will be dependent upon your current gestation at the time of the scan.

What Are Abnormal Amniotic Fluid Levels?

According to clinical guidelines, the average index level is from 5 to 25 cm (approximately 2 inches to 10 inches). However, average measurements can be 80 mm to 140 mm (3.15 inches to 5.5 inches) between the 5th and 8th months of a healthy pregnancy.

Fluid levels greater than 25 cm are considered excessive. This is called polyhydramnios. Any AFI less than 5 cm is abnormal, and this is called oligohydramnios.

1. Oligohydramnios (Low Amniotic Fluid Levels)

If you have low fluid levels, there are various causes, risks, and possible treatments to help.

Risks With Low Fluid Levels

The risks of low amniotic fluid levels in the womb include:

  • Contractures (shortening) of the limbs.
  • Clubbing of the feet and hands.
  • The potential of developing hypoplastic (underdeveloped) lungs.

When babies are born with inadequate lung capacity, they can’t get enough oxygen. This can involve severe complications and can be fatal.

What Causes It?

  • Infections.
  • The baby’s kidneys are not functioning correctly or are malformed (when the amniotic fluid volume is mostly urine in late pregnancy).
  • Procedures such as chorionic villus sampling (CVS). This test samples placental tissue and can detect a significant amount of disorders (4).
  • Preterm premature rupture of membranes (PPROM) — a medical term for preterm breaking of water.

How Is It Medically Managed?

  • Bed rest.
  • Oral fluids.
  • Intravenous hydration. This involves a short hospital stay with you on a fluid drip directly into your veins.
  • Antibiotics.
  • Steroids.
  • Amnioinfusion. This is when extra fluid is added to the amniotic sac to increase liquid levels.

Can I Do Anything to Help?

Yes, you can. Take your physician’s advice — especially regarding bed rest. Of course, they don’t mean staying horizontal in bed for the remainder of your pregnancy, but avoid all strenuous activity.

Generally, taking it easy is best. Increasing your fluid intake can help too, so drink plenty of water.

2. Polyhydramnios (High Amniotic Fluid Level)

At the opposite end of the fluid level spectrum, high amniotic fluid level is when you have too much amniotic fluid on board. Although deemed less severe than too little amniotic liquid, this complication does have associated risks (5).

Risks with Excess Fluid Levels

These are the risks of having excess amniotic fluid levels in the womb:

  • Premature labor.
  • Difficulty breathing/shortness of breath.
  • Abnormal fetal position.
  • Umbilical cord prolapse.
  • Uterine atony (lack of muscle contractions during labor).
  • Placental abruption (separation of the uterus from the placenta).
  • Abnormal positioning of the fetus (6).

I know this is serious business, but sharing is caring. I was huge in my most recent pregnancy, but just in the front. That was thanks to my chubby unborn baby and some excess amniotic fluid.

My husband made me sit on a trash bag in the car for fear of my water breaking and flooding his precious-metal baby. After reading about leaking fluid, I ended up visiting the emergency room a few times as I was convinced I was trickling my water whenever I stood up.

You’ve probably gathered by the tone that this wasn’t actually the case. I had just managed to pee myself. That was embarrassing!

Clearly, my pelvic floor wasn’t so much a floor anymore. It was more like a trap door, letting my pee escape at will. If you’ve been there, you get it! This problem isn’t uncommon among pregnant women.

What Can Cause Polyhydramnios?

  • Maternal diabetes.
  • Carrying twins or multiple babies.
  • Fetal abnormalities that prevent the baby from swallowing fluid to create urine. (This is rare.)
  • Fetal anemia caused by blood incompatibility. (This is also rare.) (7)

How Is It Medically Managed?

  • High-resolution sonograms.
  • Amniocentesis to check for infections or remove fluid by syringe. They can do this multiple times if required.
  • Non-stress tests that monitor fetal heartbeat at rest and while moving.
  • Pharmaceutical drugs. However, clinicians have raised concerns about their side effects on the baby and mother.
  • Close monitoring.

What Can I Do?

  • Try not to worry. Polyhydramnios isn’t usually a sign of something serious.
  • Keep an eye on your symptoms. Let your obstetrician know immediately if anything changes, such as abnormally rapid bump growth.
  • Rest.

Unknown Causes

If the condition’s cause is unknown, then other treatments may be used. For example, your doctor may suspect a fetal bladder obstruction. A small tube can be placed in the bladder while in utero to start the flow of fluid in the amniotic sac.

Amniotic Fluid FAQs

1. What If I Have Abnormal Fluid Levels?

Your course of action will depend on whether your AFI is too low or high for your current gestation.

If you are told during a routine sonogram that you have excess fluid in the uterus, you will be offered close monitoring of both the baby and you. You may even have fluid removed via a syringe.

If you have levels on the lower end of the scale, you may be required to stay in the hospital to receive hydration, amniotic infusions, etc.

If you go into labor and have known abnormal AFI, be prepared that you may be asked to go into the hospital immediately.

2. Are There Possible Treatments?

Unfortunately, there aren’t many effective treatments for either oligohydramnios or polyhydramnios. It is usually managed conservatively.

If your sonographer has any concerns during your routine checks, they’ll know what to do. Working closely with your doctor, they will do everything to keep you and your little one safe.

3. What Are Signs of Leaking Fluid?

People will probably say, “Don’t panic; you’ll know when it happens!” The fact is, a lot of moms, and not just first-time moms, don’t know what to expect at all.

The main sign of fluid loss is a gush or constant trickle of odorless, clear, or straw-colored fluid. Most women have the trickling symptom rather than a large gush of fluid.

This is what to do if you suspect fluid loss:

  • Write down the time it happened.
  • Try guessing how much fluid you see (such as a glass full).
  • Take note of whether it’s a continuous leak or small bits at a time.
  • Evaluate how the fluid appears.
  • Wear a pad to monitor the fluid easily.
  • Call your doctor. This needs to be checked out.
  • Do not use tampons or insert anything into the vagina.

Beware that if a fluid leak is confirmed, your labor may start at any time. In fact, most doctors indicate that you may need to be induced to deliver your baby because of the risk of infection.


Conclusion

From the moment you are pregnant until the moment you give birth, you will undoubtedly worry about every eventuality. Reading up too much on risks in pregnancy can drive you crazy. If you have any concerns, never be afraid to speak with your obstetrician or midwife, who will gladly put your mind at ease.

If you are diagnosed with polyhydramnios or oligohydramnios, you can manage, but the condition cannot be cured.

Leaking amniotic fluid comes out continuously. But leaking urine generally happens when you’re laughing, coughing, or sneezing, and it isn’t constant.

Get in touch with your health provider if you need reassurance, even if you end up embarrassed. It’s better to be safe than to risk potential complications.

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Headshot of Caitlin Goodwin, MSN, RN, CNM

Medically Reviewed by

Caitlin Goodwin, MSN, RN, CNM

Caitlin Goodwin MSN, RN, CNM is a Certified Nurse-Midwife, clinical instructor and educator. She has ten years of nursing experience and enjoys blogging about family travel and autism in her free time.