Diagnosis

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.