Your Complete Guide to Amniotic Fluid Levels During Pregnancy

Last Updated: September 28, 2023
Liesel Teen, RN-BSN

By Liesel Teen

BSN, RN, Practicing Labor and Delivery Nurse

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Hi mama! Did you know amniotic fluid levels are SERIOUSLY important to how well your baby can recirculate waste? It’s something we watch carefully during pregnancy.

If there are any concerns, your doctor will estimate this amount to ensure that you don’t have too little or too much amniotic fluid.

Are you here because you’ve have irregular amniotic fluid levels? Don’t stress out about this one, guys! Your doctor will let you know when to worry.

If you have low or high amniotic fluid levels, there’s still hope! While either can have significant consequences if left untreated, both conditions can be dealt with.

Take the time to learn more below so you know all the right questions to ask.

What is the Amniotic Fluid Index?

The amniotic fluid index (AFI) is the estimated range of possible volume of fluid in the amniotic sac. We’ll get into the specifics in a minute, but be aware that this number is usually VERY important in pregnancy.

Why is the Amniotic Fluid Index Important?

The amount of fluid helps indicate how healthy the baby is in utero. To check it, doctors measure amniotic fluid levels around the baby. Then, they either add up estimates of four separate quadrants or they measure the “single deepest pocket”.

Amniotic fluid levels that are too high are called polyhydramnios. If the level is too low, it’s called oligohydramnios. Both instances can result in premature birth, birth defects, or even stillbirth.

While LOW amniotic fluid is probably why most of you are here, HIGH amniotic fluid is also definitely a problem.

To ease your worries – too high or too low amniotic fluid levels and normal delivery CAN go hand in hand. Luckily there are treatments to take care of either condition.

Amniotic Fluid Index Calculation

The normal amniotic fluid level range is between 8 to 18 cm. How that’s measured differs from provider to provider. There are two go-to tests that are equally accurate.

  • The first method is to estimate the depth of volume in each of the four quadrants within the placenta. Then add them as if stacked top to bottom
  • The second method is to estimate the “single deepest pocket range” or “deepest vertical pocket” method. Your provider will find the pocket with the most vertical volume and record that value from top to bottom

Normal Amniotic Fluid Volume (in ml)

These seem like they would give drastically different results. But actually, the acceptable amount of volume averages out easily between the hoped-for 8 -18 centimeters.

As you can expect, a quadrant measurement is going to be on the high end. Whereas a single deepest measure will be on the low end. This is why there’s such a wide range.

Regardless of which way your care provider goes, you can have faith in the results and put your knowledge in the game.

Amniotic fluid levels by trimester

Now…are you wondering if there is amniotic fluid during ALL trimesters of pregnancy?

  • First Trimester amniotic fluid levels: Amniotic fluid is pretty negligible during the first trimester.
  • Second Trimester amniotic fluid levels: Amniotic fluid reaches a median (the middle line, or consistent average) right around 20 weeks
  • Third trimester amniotic fluid levels: Most of the third trimester sees the amniotic fluid levels staying consistent. Then right around week 35 or so the fluid begins to decline in preparation for delivery

This means, irregularities will likely be spotted sometime between weeks 20 and 35. That’s because this is when it levels out.

For this reason, be sure to remember to ask about your fluid levels during your anatomy scan, which should happen right around that 20-week mark.

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High Amniotic Fluid Levels

When amniotic fluid levels are high, it’s called polyhydramnios.

It’s not typically diagnosed until it’s at about 24-25 cm if measured by the quadrant method or 8 cm if by the deepest pocket method.

Polyhydramnios occurs in about 1-2% of pregnancies.

Symptoms of polyhydramnios can be shortness of breath and swelling in the lower body. Polyhydramnios can lead to preterm labor and/or breech positioning (among other things).

What Causes Polyhydramnios

It isn’t always clear why polyhydramnios levels happen.

Doctors do acknowledge that polyhydramnios can result from:

  • A birth defect already present in the baby
  • Complications resulting from having twins
  • Anemia in the infant’s blood
  • Infections
  • Gestational diabetes
  • Incompatibilities in blood type between the fetus and the mama

Polyhydramnios Diagnosis

Your doctor will usually spot high fluid levels during your 20 week ultrasound.

This scan isn’t always performed by your OB/GYN. A lot of institutions look to a specialist in ultrasound, so be sure to carry your concerns with you when you go.

How to Reduce Amniotic Fluid Levels During Pregnancy

High amniotic fluid level treatment is entirely possible, and your doctor will ensure that your needs are taken care of even if you don’t think to ask.

Treatments include draining excess fluids through a process called amniocentesis. There are also medications that can help trigger the body to reduce the production of fluids. Keep in mind that these may not be safe in the third trimester.

Low Amniotic Fluid Levels

When amniotic fluid levels fall too low, it’s called oligydramnios. It’s determined by less than 2cm when measured with the “single deepest pocket” method, or 5cm when viewed on the quadrant method scale. Oligohydramnios is more common than polyhydramnios, occurring in about 4% of pregnancies.

When amniotic fluid levels are low or borderline low early in pregnancy, that pregnancy is in danger, and it’s important to involve your healthcare provider or follow their medical advice immediately.Once you reach the third trimester, momma, you can put any fear of this off to the back burner. There are still risks of premature birth or even stillbirth, but the latter will likely connect with other more serious symptoms.

Low amniotic fluid at 34 weeks, for example, still potentially puts the mother at risk for preterm labor, but the baby is potentially viable by then, so the risk is much less if all else seems normal.

What Causes Oligohydramnios?

Preexisting conditions can contribute to low amniotic fluid levels. High blood pressure and medications that treat it can have an impact, as well as birth defects or a late-term pregnancy (any pregnancy that goes past 39 weeks or so).

Beyond that, you can naturally fit amniotic fluid leakage into the mix. That’s when your water breaks before you actually go into labor. This one shouldn’t last long, as it is VITAL that you get to the hospital ASAP to avoid infection and get labor on the way.

Oligohydramnios Diagnosis

Some things to watch out for are a smaller measurement than what would be normal for the baby’s gestational age, less weight gain, a decrease in fetal movement.

Unfortunately, there’s really no clear red flag, so you’ll have to rely heavily on your care provider.

How to Increase Amniotic Fluid Levels During Pregnancy

The biggest things that can help with oligohydramnios treatment are increasing your intake of fluids, especially water, and getting more rest.If you’re earlier in your pregnancy where risks are greater, your doctor might opt to introduce saline solution into the uterus.

Amniotic Fluid Levels and the Fluid Index in Your Pregnancy

As a practicing labor and delivery nurse, amniotic fluid is a DAILY consideration for me.

Sure, a lot of the action regarding amniotic fluid apply more to what happens before you get onto my bed, mama. However, the reality is that artificial rupture of membranes (AROM) is a common procedure used during labor management and one that has been used for hundreds of years (source).

It’s called amniotomy, and it’s messy.

The purpose is to evacuate the fluid within the sac in order to precipitate childbirth – because when the bath tub is empty, it’s time to get out.

Obviously, there’s more to inducing labor than that, but it’s the first step toward childbirth that is mandatory to get the ball rolling.

What can you do to monitor your amniotic fluid levels?

But before perforation, before delivery day, the most important thing you can do for yourself is to ensure that you are getting to your regular prenatal well checks and having an open dialog with your care provider.

Whether you’re worried about oligohydramnios or polyhydramnios, you’ll be in great shape as long as you know the right questions to ask and take the time to understand your options.

Amniotic fluid levels are an important measure of the health of your baby and a good predictor for potential complications. This way, your chosen team is ready and prepared to take the very best care of your tummy and your kiddo.

Happy baby making!

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Liesel Teen, RN-BSN

Liesel Teen

BSN, RN, Practicing Labor and Delivery Nurse

As a labor and delivery nurse, I’ve spent countless hours with women who felt anxious — even fearful — about giving birth. I want you to know it doesn’t have to be that way for you!

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