What Low Amniotic Fluid Could Mean for Your Pregnancy

Learned that your amniotic fluid levels are low? Here’s what that means for you and baby and how you can address it.
ByChristian Pope, DO, FACOG
OB-GYN
Updated
Jul 2020
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Photo: Paul Venning

So, you had an ultrasound and learned that the amniotic fluid around baby is low. What does that mean? It’s an intricate answer. It depends how low the fluid volume is, how far along in pregnancy you are and what the possible cause of the low fluid may be. Amniotic fluid is essential for the normal growth, development and well-being of your baby, and identifying low amniotic fluid is an important part of prenatal care. Read on to learn what low amniotic fluid could mean for your pregnancy and what you can do to get the levels up.

What is Amniotic Fluid?

Amniotic fluid is the liquid in the amniotic sac that surrounds, protects, and nurtures your growing baby. It prevents the umbilical cord from being compressed and keeps baby’s environment at a stable temperature; it’s also what baby breathes and swallows in utero, supporting the development of the lungs and digestive system.

Experts aren’t sure about where amniotic fluid in the first trimester comes from, but one plausible theory is that the fluid comes from both Mom and baby. Beginning in the second trimester, baby is the primary producer of amniotic fluid. The volume is maintained by a balance of fluid production from baby’s lungs and urine and fluid reabsorption from the baby swallowing and fluid flow across the placenta. This constant flow of water (and nutrients) in and out of the amniotic fluid sac maintains a special electrolyte balance that’s essential for fetal development.

By the end of pregnancy, baby’s urine is the primary source of amniotic fluid, with amounts varying from 400 to 1200 milliliters per day at term. Baby’s lungs are the secondary source of amniotic fluid, where they secrete approximately 350 milliliters of fluid per day at term.

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One of the many roles of amniotic fluid is to help cushion and protect the umbilical cord. If you have low amniotic fluid, there’s a risk the umbilical cord may become compressed, which can be dangerous. That’s why doctors like to make sure your amniotic fluid levels are normal. We do this by making certain your uterine growth corresponds with how many weeks along you are at your prenatal visits, called fundal height checks. Additionally, ultrasound is used to measure amniotic volume.

There’s a certain amount of amniotic fluid that’s needed during pregnancy. This is called the “amniotic fluid index,” or more recently termed “maximal vertical pocket” (MVP). Amniotic fluid levels should range between 5 and 23 cm in overall measured volume, or greater than 2 cm MVP in the late second and third trimesters.

If your amniotic fluid levels are hovering around 5 cm, we begin to get concerned. Your doctor will likely perform some additional monitoring with nonstress tests and follow-up ultrasound. When the amniotic fluid volume is less than 5 cm, or the MVP is less than 2 cm, it’s classified as oligohydramnios, a condition of low amniotic fluid that can be a risk to the baby. If you’re term or close to term, delivery is usually recommended. If baby is still premature, close monitoring with fetal testing is done, together with encouraging plenty of fluids to help try and replenish your hydration and therefore baby’s hydration status.

If your amniotic fluid levels are around 6 or 7 cm, your doctor may tell you that your fluid volume is “low normal.” I realize that this often just creates anxiety and worry. However, the low normal term simply means your doctor will recheck your amniotic fluid volume again in a week or so to make sure it’s trending in the right direction. So don’t worry.

Low amniotic fluid levels aren’t common in the second and early third trimester but become more prevalent as moms-to-be approach their due date and especially post-term (after 40 weeks). Therefore, should you pass your due date, your doctor will likely measure your amniotic fluid by ultrasound to make sure it remains normal.

What Causes Low Amniotic Fluid?

Low amniotic fluid levels, termed oligohydramnios, affects about 1 to 5 percent of all pregnancies and occurs most commonly with the following pregnancy conditions:

  • Premature rupture of membranes (when your water breaks)
  • Post term pregnancy
  • Identical twins pregnancy
  • Maternal dehydration
  • Intrauterine fetal growth restriction ( IUGR)
  • Fetal chromosomal and congenital kidney anomalies
  • High blood pressure in pregnancy

What are the Risks of Low Amniotic Fluid?

The risks of low amniotic fluid really are dependent on when in pregnancy the volumes are low. Since baby’s limbs, skin and lungs are developing early in the second trimester, low amniotic fluid during this time may cause problems with proper development, causing poor and improper lung development called pulmonary hypoplasia.

Additionally, when your water breaks—which is when your amniotic sac releases amniotic fluid through a torn membrane—there’s an increased risk of infection. If this happens when you’re term, delivery is recommended. If it happens before week 37 (also known as preterm premature rupture of the membranes), the decision is individualized based on baby’s gestational age.

Finally, amniotic fluid plays an important role in the cushioning of the umbilical cord within the uterus. If you have low amniotic fluid, the umbilical cord may become compressed, which in turn can compromise baby’s oxygen levels and, rarely, lead to fetal death if the cord is completely blocked.

Signs of Low Amniotic Fluid

Low amniotic fluid is diagnosed by ultrasound, although an ob-gyn may be able to identify signs of low amniotic fluid if they observe quick drops in baby’s fetal heart rate during a monitoring period. This is due to quick, temporary compressions of the umbilical cord. Of course, you can’t do either of those things on your own at home. So what are the signs of low amniotic fluid you can be on the lookout for?

If your amniotic fluid levels are low, you may feel less fetal movement, since baby needs an adequate amount of amniotic fluid to move around in. You may also notice that you’re leaking amniotic fluid vaginally. Signs of leaking amniotic fluid are usually a gush of clear, watery fluid from the vagina that doesn’t stop. However, symptoms can vary from very slight leakage that’s difficult to notice, to an obvious large gush of fluid that soaks through your clothes.

What does amniotic fluid look like?

Amniotic fluid is typically a clear, odorless fluid. However, it may also have a sweet smell to it at times. It’s not thick or mucousy, but it may occasionally be blood-tinged.

What to do if you’re leaking amniotic fluid

It all depends on what kind of fluid you’re leaking (is it amniotic fluid, urine or increased vaginal discharge?), and often it’s hard to figure out—so don’t try to diagnose yourself. Call your doctor.

In about 8 percent of pregnancies, women will break their water before going into labor, which is called premature rupture of membranes. This can be either a gush or a trickle of warm, clear amniotic fluid that doesn’t stop, sometimes followed by the onset of contractions. Some women describe it as feeling a little wet or like they’ve peed their pants. If you think you’re leaking amniotic fluid, call your doctor right away. That’s because if you’ve broken your water, you need to be admitted to the hospital.

Here are some helpful tips to help you decide at 2 a.m. what the liquid may be and whether you should wake up your doctor:

Likely amniotic fluid:

  • Large gush of clear, warm fluid that doesn’t smell like urine
  • Warm fluid that continues to flow, especially with standing and position-changes
  • Constant leaking, even a little bit of clear fluid
  • Fluid that’s blood-tinged
  • Large amount of warm fluid that is green/brown in color (this is called meconium)

Unlikely amniotic fluid:

  • Thick white or yellow discharge
  • Thin yellowish or clear discharge
  • Small amount of yellow warm fluid that smells like urine (because it is)
  • Discharge that’s itchy

If you’re ever unsure whether you’re leaking amniotic fluid, call your doctor.

How to Increase Amniotic Fluid

Hydrate, hydrate, hydrate! We know that a major component of amniotic fluid is water. This water comes from both Mom and baby. The more well-hydrated the mother is, the more well-hydrated the fetus is. Especially for cases of low amniotic fluid levels due to maternal dehydration, drinking more water will help. If for some reason oral rehydration doesn’t work, sometimes intravenous hydration of a few liters of fluid may do the trick.

About the expert:

Christian Pope, DO, FACOG, is a board-certified obstetrician and gynecologist and fellow of the American College of Obstetricians and Gynecologists in private practice at Hawthorn Medical Associates in Massachusetts. He is also a medical staff member at St. Luke’s Hospital of Southcoast Hospitals and at Women and Infants’ Hospital in Providence, Rhode Island. Additionally, he serves as a clinical instructor of obstetrics and gynecology at the Warren Alpert Brown University School of Medicine. A graduate of the Philadelphia College of Osteopathic Medicine, Pope received his obstetrics and gynecology training at the Tufts University School of Medicine, Baystate Medical Center.

Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.

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