What is Polyhydramnios?

When you become pregnant, you're likely prepared to gain some weight. But you might not expect some of that weight to be excess amounts of amniotic fluid. In fact, you might not have ever heard of polyhydramnios, a condition that occurs when you have too much amniotic fluid—but it is something to be aware of in order to spot the symptoms.

During pregnancy, a slightly yellowish fluid surrounds the fetus inside your uterus, allowing the baby to move, grow, and stay safe. It’s constantly adjusting, too, because your baby consumes the fluid and then expels it in an ongoing cycle. You’ll almost certainly hear someone jokingly call it “baby pee,” which isn’t entirely inaccurate, as your baby’s urine actually does comprise most of the fluid by about 20 weeks of pregnancy. Despite the fact that amniotic fluid is important, you can have too much of it, and that’s called polyhydramnios. 

Polyhydramnios is essentially an excessive amount of amniotic fluid. What that means in practical terms is that there’s too much amniotic fluid surrounding your baby in utero. The opposite of polyhydramnios is called oligohydramnios, which refers to an unusually low amount of amniotic fluid. 

If you are diagnosed with polyhydramnios, the good news is that you don’t necessarily need to worry about experiencing any major complications during the rest of your pregnancy.  “The majority of polyhydramnios happens in the third trimester, and it is usually mild,” says Mara Rosner, MD, a fetal therapy specialist with the Johns Hopkins Center for Fetal Therapy and an assistant professor of gynecology and obstetrics with Johns Hopkins Medicine.

Symptoms of Polyhydramnios

You might not have any idea that you’ve developed polyhydramnios, but some pregnant people do experience some symptoms. Some signs to watch out for include:

• Breathlessness or a short-of-breath feeling
• Constipation
• Heartburn
• Swollen feet and ankles

Diagnosis

There are two ways to measure or quantify the amount of amniotic fluid in your body. The first is called the amniotic fluid index, or AFI. The second measurement is called dingle deepest pocket (SDP).

Amniotic Fluid Index (API)

A technician will use an ultrasound wand to assess the fluid levels in four quadrants of the uterus, before adding them together and dividing by four. A normal level of amniotic fluid is 5 to 25 cm. If your amniotic fluid is higher than that, it’s considered polyhydramnios. 

Single Deepest Pocket (SDP)

In this method, the ultrasound technician will look for the deepest single pocket of amniotic fluid and measure that. A normal level is 2 to 8 cm for this approach. If the amount of amniotic fluid exceeds 8 cm, you may have polyhydramnios. 

Causes of Polyhydramnios

Research suggests that less than 2% of pregnancies meet the criteria for a polyhydramnios diagnosis. Sometimes, doctors don’t even know what causes it, so they refer to it as idiopathic polyhydramnios. 

"Many times, when we see a patient with polyhydramnios, we don't know why they have it," Dr. Rosner says. However, there are some conditions that are associated with an increased risk. 

For example, if you have gestational diabetes, you may be at elevated risk for excessive amniotic fluid. The good news is that if you do have gestational diabetes and you develop polyhydramnios, it will likely be a mild case. And some research suggests that gestational diabetes may be less of a contributing factor than previously thought. 

Other possible risk-factors include a pregnancy with multiples, a blockage in the baby’s gut, an infection during pregnancy, and certain genetic conditions. Rhesus disease can also be a potential cause. This is a condition that develops when antibodies in the pregnant person’s blood attack the fetus’ blood cells. 

Risks Associated with Polyhydramnios

Pregnant people with polyhydramnios may be at increased risk for a longer first stage of labor. Research also suggests that you are at increased risk for needing to undergo a cesarean section. This condition can also be associated with fetal distress and increased need for admission to the neonatal intensive care unit.

“During labor, it is important to be vigilant about the possibility of cord prolapse,” says Kecia Gaither, MD, an OB/GYN and maternal fetal medicine specialist, and director of perinatal services at NYC Health + Hospitals/Lincoln.

However, this may reassure you: “The majority of women who are diagnosed with isolated polyhydramnios, meaning there is no other known issue with the baby, are going to have an excellent outcome,” says Dr. Rosner.

If you are pregnant with monochorionic twins—that is, twins who share a single placenta–you should be aware of the clinical signs of polyhydramnios, like abdominal fullness and a sudden increase in abdominal girth. “That can be a sign of developing twin-to-twin transfusion syndrome, and you should call your doctor immediately,” says Dr. Rosner, referring to a condition in which one twin receives the majority of the fetal blood flow at the expense of the other twin.

She adds, “That should be taken very seriously, and they should be referred for an ultrasound as soon as possible.” 

Treatment of Polyhydramnios

After your diagnosis, your doctor might request some additional visits and ultrasound scans to check on your baby. “Management is predicated on the underlying case and the severity of the polyhydramnios,” explains Dr Gaither. 

For example, if your polyhydramnios seems to be the result of gestational diabetes, you’ll need to take care to appropriately manage your blood sugar levels, which may include dietary changes and medications.

One possible treatment is a procedure called an amnioreduction, which involves draining some of the excess fluid, sometimes with the use of a vacuum-assisted aspiration device, which is generally considered a safe procedure with low complication rates. 

Dr. Rosner says she would consider offering an amnioreduction to a patient with severe polyhydramnios, particularly if the patient can't lie flat or breathe comfortably due to the excess amounts of amniotic fluid. “But those are very rare cases,” she assures. 

Coping with Polyhydramnios

If you know you’re at risk for developing polyhydramnios—for example, maybe you have gestational diabetes—talk to your OB/GYN or healthcare prvide about watching for signs. And if you do receive a diagnosis, be sure to have a conversation about preparing for your eventual labor and delivery. 

A Word from Verywell

It can be unnerving to learn that you have a condition during pregnancy that could have adverse outcomes. In the case of polyhydramnios, it may be helpful to remember that there’s nothing you could have done to prevent this condition from occurring. You just need to learn more about how to proceed. Make sure to talk about your concerns with your OB/GYN or healthcare provider. Ask how they plan to monitor your amniotic fluid levels and what to expect when it’s time to deliver your baby.