Low Amniotic Fluid: Causes, Symptoms, Diagnosis, and Treatment

If you've been diagnosed with low amniotic fluid or have symptoms of it, such as decreased fetal movement, you likely have many concerns. You may be wondering what this means for you and your unborn baby. You may also wonder what it means for your pregnancy. How is low amniotic fluid treated, for example? What happens when you receive this diagnosis?

The good news is low amniotic fluid in pregnancy, or oligohydramnios, is relatively uncommon. It is also highly treatable. Infants born after living in these conditions have favorable outcomes. But learning something is amiss can be startling, which is why we reached out to OB-GYNs to help us understand what low amniotic fluid is, and what it means for expectant parents.

What Is Amniotic Fluid?

Amniotic fluid is the fluid that your unborn baby floats in in the womb, and it's what is released when your water breaks. Amniotic fluid has some specific purposes. It protects the fetus from infections and cushions it from external pressures and blows. Amniotic fluid helps your unborn baby's respiratory and digestive system develop, and it regulates their body temprature. The fluid insulates the fetus, keeping it warm.

The amount of amniotic fluid in the womb changes over time. It increases steadily as your baby grows, reaching a peak volume at about 34 to 36 weeks gestation. At that point, it starts to level off, slowly decreasing as delivery approaches. As such, the amount of amniotic fluid you have toward the end of pregnancy is naturally on the low side.

What Causes Low Amniotic Fluid, or Oligohydramnios?

The causes of low amniotic fluid vary based on where you are in your pregnancy. In early pregnancy, the causes usually have to do with a health problem in the pregnant parent or the fetus. According to Adi Davidov, M.D, associate chair and director of obstetrics and gynecology at Staten Island University Hospital, common medical causes include fetal kidney abnormalities, placental problems, and fetal growth restriction. Toward the end of pregnancy, when low amniotic fluid is more common, the decreased levels may be related to a pregnant person's water breaking early, or a pregnancy that is past term, Dr. Davidov explains.

Priyanka Venkataraman, M.D, OB-GYN, says that whatever the cause of low amniotic fluid, it should be taken seriously. "Basically, if noted, this requires additional work up, close monitoring, and possibly delivery," she explains.

How Common Is Oligohydramnios?

Low amniotic fluid impacts about 4.4% of pregnancies, though it's less common in preterm pregnancies, impacting only 1% of these. This is a similar range as what Dr. Venkataraman sees in her practice. "I have noticed this in 2 to 3 out of 20 pregnancies, usually in the third trimester," she shares. "It is very rarely noted earlier in the pregnancy, in which case it could mean a structural abnormality with the fetus," she adds.

What Are the Symptoms of Low Amniotic Fluid?

The main symptom of low amniotic fluid is decreased fetal movement, says Dr. Davidov. "The parent may feel their unborn baby move less than usual," he adds. However, it's important to note that that is not always the case. In many instances, expectant parents do not experience any clear symptoms. This means that you could have low amniotic fluid without realizing it.

Dr. Venkataraman agrees that decreased fetal movement is a possible symptom, and is usually the first sign that is noticed. "When there is less fluid, it restricts the space the fetus can move in," she explains. Another possible sign of low amniotic fluid is that your belly will measure smaller than expected according to how far along you are, Dr. Venkataraman adds.

How Is Low Amniotic Fluid Diagnosed?

Of course, symptoms like decreased fetal movement don't always indicate that you have low amniotic fluid. To find this out for sure, your healthcare provider will need to do some diagnostic testing. According to the American College of Obstetricians and Gynecologists (ACOG), the tests commonly used to measure amniotic fluid include ultrasounds, biophysical profiles, and non-stress tests.

Ultrasounds are used to diagnose low amniotic fluid by "either measuring the greatest vertical pocket of amniotic fluid or calculating an amniotic fluid index," Dr. Davidov describes. Another way to say this is that ultrasounds are able to assess and quantify the amount of amniotic fluid surrounding the fetus, as Dr. Venkataraman explains it.

Usually, ultrasounds to assess amniotic fluid are part of the biophysical profile that examines fetal wellbeing and is often performed in high risk pregnancies, says Dr. Venkataraman. These are done in the third trimester. "If an abnormal result is noted, it may require additional testing, closer monitoring, or even delivery depending on how far along the pregnancy is," Dr. Venkataraman explains.

What Is the Treatment for Oligohydramnios?

Treatment for low amniotic fluid will depend on the cause, as well as how far along you are in your pregnancy. "In most cases, when the patient is close to their due date, we deliver the baby," says Dr. Davidov. "In instances earlier in the pregnancy, we monitor the unborn child's health and deliver if there are any worrisome findings." However, there are no specific treatments to increase amniotic fluid, Dr. Venkataraman adds.

"This is most likely an indicator of stress to the pregnancy, requiring additional work up, monitoring, intervention for the underlying stressor, including possibility of delivery," she describes. Some research indicates that drinking extra fluids can increase amniotic fluid—especially during the third trimester—but it's unclear how much this may help.

The Bottom Line

The good news is that low amniotic fluid is a relatively rare diagnosis, and it usually happens during the third trimester when your unborn baby can be safely delivered. If you think you might be dealing with a case of low amniotic fluid, you should contact your healthcare provider.

Importantly, one of the main signs of low amniotic fluid—decreased fetal movement—is something you should take seriously regardless of the cause. Contact your healthcare provider right away if you notice less movement.

You should also contact your provider immediately if you develop a fever above 100.4°F, have sudden, intense cramping or contractions, experience a severe headache, have blurred vision, or experience any type of fluid leaking from your vagina.