Polyhydramnios (pol-e-hi-DRAM-nee-os) is the excessive accumulation of amniotic fluid — the fluid that surrounds the baby in the uterus during pregnancy. Polyhydramnios occurs in about 1 to 2 percent of pregnancies.

Most cases of polyhydramnios are mild and result from a gradual buildup of amniotic fluid during the second half of pregnancy. Severe polyhydramnios may cause shortness of breath, preterm labor, or other signs and symptoms.

If you're diagnosed with polyhydramnios, your health care provider will carefully monitor your pregnancy to help prevent complications. Treatment depends on the severity of the condition. Mild polyhydramnios may go away on its own. Severe polyhydramnios may require closer monitoring.

Polyhydramnios symptoms result from pressure being exerted within the uterus and on nearby organs.

Mild polyhydramnios may cause few — if any — signs or symptoms. Severe polyhydramnios may cause:

• Shortness of breath or the inability to breathe
• Swelling in the lower extremities and abdominal wall
• Uterine discomfort or contractions
• Fetal malposition, such as breech presentation

Your health care provider may also suspect polyhydramnios if your uterus is excessively enlarged and he or she has trouble feeling the baby.

Some of the known causes of polyhydramnios include:

• A birth defect that affects the baby's gastrointestinal tract or central nervous system
• Maternal diabetes
• Twin-twin transfusion — a possible complication of identical twin pregnancies in which one twin receives too much blood and the other too little
• A lack of red blood cells in the baby (fetal anemia)
• Blood incompatibilities between mother and baby
• Infection during pregnancy

Often, however, the cause of polyhydramnios isn't clear.

Polyhydramnios is associated with:

• Premature birth
• Premature rupture of membranes — when your water breaks early
• Placental abruption — when the placenta peels away from the inner wall of the uterus before delivery
• Umbilical cord prolapse — when the umbilical cord drops into the vagina ahead of the baby
• C-section delivery
• Stillbirth
• Heavy bleeding due to lack of uterine muscle tone after delivery

The earlier that polyhydramnios occurs in pregnancy and the greater the amount of excess amniotic fluid, the higher the risk of complications.

If your health care provider suspects polyhydramnios, he or she will do a fetal ultrasound. This test uses high-frequency sound waves to produce images of your baby on a monitor.

If the initial ultrasound shows evidence of polyhydramnios, your health care provider may do a more detailed ultrasound. He or she will estimate the amniotic fluid volume (AFV) by measuring the single largest, deepest pocket of fluid around your baby. An AFV value of 8 centimeters or more suggests polyhydramnios.

An alternative way of measuring amniotic fluid is measuring the largest pocket in four specific parts of your uterus. The sum of these measurements is the amniotic fluid index (AFI). An AFI of 25 centimeters or more indicates polyhydramnios. Your health care provider will also use a detailed ultrasound to diagnose or rule out birth defects and other complications.

Your health care provider may offer additional testing if you have a diagnosis of polyhydramnios. Testing will be based on your risk factors, exposure to infections and prior evaluations of your baby. Additional tests may include:

• Blood tests. Blood tests for infectious diseases associated with polyhydramnios may be offered.
• Amniocentesis. Amniocentesis is a procedure in which a sample of amniotic fluid — which contains fetal cells and various chemicals produced by the baby — is removed from the uterus for testing. Testing may include a karyotype analysis, used to screen the baby's chromosomes for abnormalities.

If you're diagnosed with polyhydramnios, your health care provider will closely monitor your pregnancy. Monitoring may include the following:

• Nonstress test. This test checks how your baby's heart rate reacts when your baby moves. During the test, you'll wear a special device on your abdomen to measure the baby's heart rate. You may be asked to eat or drink something to make the baby active. A buzzer-like device also may be used to wake the baby and encourage movement.
• Biophysical profile. This test uses an ultrasound to provide more information about your baby's breathing, tone and movement, as well as the volume of amniotic fluid in your uterus. It may be combined with a nonstress test.

Mild cases of polyhydramnios rarely require treatment and may go away on their own. Even cases that cause discomfort can usually be managed without intervention.

In other cases, treatment for an underlying condition — such as diabetes — may help resolve polyhydramnios.

If you experience preterm labor, shortness of breath or abdominal pain, you may need treatment — potentially in the hospital. Treatment may include:

• Drainage of excess amniotic fluid. Your health care provider may use amniocentesis to drain excess amniotic fluid from your uterus. This procedure carries a small risk of complications, including preterm labor, placental abruption and premature rupture of the membranes.
• Medication. Your health care provider may prescribe the oral medication indomethacin (Indocin) to help reduce fetal urine production and amniotic fluid volume. Indomethacin isn't recommended beyond 31 weeks of pregnancy. Due to the risk of fetal heart problems, your baby's heart may need to be monitored with a fetal echocardiogram and Doppler ultrasound. Other side effects may include nausea, vomiting, acid reflux and inflammation of the lining of the stomach (gastritis).

After treatment, your doctor will still want to monitor your amniotic fluid level approximately every one to three weeks.

If you have mild to moderate polyhydramnios, you'll likely be able to carry your baby to term, delivering at 39 or 40 weeks. If you have severe polyhydramnios, your health care provider will discuss the appropriate timing of delivery, to avoid complications for you and your baby.

Polyhydramnios can be a worrisome finding during pregnancy. Work with your pregnancy care provider to ensure that you and your baby receive the best possible care.

You're likely to start by talking with your pregnancy care provider. Here's some information to help you get ready for your appointment and what to expect from your doctor.

What you can do

Before your appointment:

• Write down any symptoms you're experiencing, including when they first started and how they've changed over time.
• Write down key personal information, including any other medical conditions for which you're being treated.
• Make a list of all medications, vitamins or supplements that you're taking.
• Ask a friend or family member to accompany you, if possible, to your appointment. Having someone else there may help you remember something that you forgot or missed.
• Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. For polyhydramnios, some basic questions to ask include:

• What kind of tests do I need? How soon do I need to be tested?
• What treatment approach do you recommend?
• Do I need to follow any activity restrictions?
• What emergency signs and symptoms should I watch for at home?
• How could this condition affect my baby?
• If I get pregnant again, will this happen again?
• Do you have any printed information that I can take with me? What websites do you recommend for more information?

What to expect from your doctor

Your doctor will likely perform a physical exam and run some tests, including an ultrasound exam. He or she may also ask you a number of questions, such as:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• Do you have shortness of breath?
• Are you experiencing any lightheadedness or dizziness?
• Have you noticed an increase in swelling? Does it seem like you're retaining more fluid than usual?
• What, if anything, seems to make your symptoms better?
• What, if anything, appears to worsen your symptoms?