When a woman becomes pregnant, a sac forms around her growing baby. This sac, called the amniotic sac, is filled with fluid (amniotic fluid) that:

  • Cushions and protects the baby.
  • Helps the baby’s lungs and gastrointestinal tract grow.
  • Allows the baby to move around, which helps the baby’s muscles and bones develop.

Polyhydramnios means that there is too much fluid in the sac. Babies born with polyhydramnios should be checked for birth defects.

Polyhydramnios is too much amniotic fluid, defined quantitatively as a single deepest vertical pocket measurement greater than 8 cm or total AFI of greater than 24 cm.

Polyhydramnios may be idiopathic (in up to 40%), secondary to maternal factors such as diabetes and hypertension, or secondary to fetal factors including anything that might impair fetal swallowing of amniotic fluid (upper gastrointestinal tract obstruction, chest narrowing or mass, and severe central nervous system abnormalities) and fetal hydrops.

What are the causes?

This condition may be caused by:

  • Diabetes in the mother.
  • The baby being larger than normal for the baby’s age (large for gestational age).
  • Problems that prevent the fetus from swallowing amniotic fluid. These may include:
    • An abnormal chromosome.
    • Abnormality in the baby’s intestinal tract.
    • A birth defect in which the baby does not have a brain or parts of the brain (anencephaly).
  • A condition that affects twins, called twin-twin transfusion syndrome.
  • An illness in the mother, such as kidney or heart disease.
  • A tumor of the placenta (chorioangioma).
  • An infection in the baby.

What are the symptoms?

Symptoms of this condition include:

  • A uterus that is larger than it should be for the stage of pregnancy.
  • Shortness of breath.
  • Increased feeling of pressure on the abdomen.
  • Increased swelling in the legs.
  • Preterm labor.
  • Preeclampsia.

How is this diagnosed?

This condition may be diagnosed based on:

  • A measurement of your abdomen. Your health care provider can diagnose the condition if he or she measures you and notices that your uterus is larger than it should be.
  • An ultrasound. This image may be taken by placing a device on your abdomen or into your vagina. The test can measure the amount of fluid in the amniotic sac (amniotic fluid index). It can also:
    • Show if you are carrying twins or more.
    • Measure the growth of the baby.
    • Look for birth defects.

How is this treated?

This condition is treated by removing fluid from the amniotic sac. This is done through a procedure where a needle is inserted through the skin into the uterus (amniocentesis).

Follow these instructions at home:

  • Make sure to keep any medical conditions you have under control. If you have diabetes, talk to your health care provider about ways to manage your blood sugar.
  • Keep all your prenatal visits as told by your health care provider. It is important to follow your health care provider’s recommendations.

Contact a health care provider if:

  • You think your uterus has grown too fast in a short period of time.
  • You feel a great amount of pressure in your pelvis and are more uncomfortable than expected.

Get help right away if:

  • You have a gush of fluid or are leaking fluid from your vagina.
  • You stop feeling the baby move.
  • You do not feel the baby kicking as much as usual.
  • You have diabetes and you have a hard time keeping it under control.
  • You have kidney or heart disease and it is causing you problems.


  • Polyhydramnios means there is too much fluid in the amniotic sac. This can lead to birth defects.
  • This condition may be diagnosed based on a measurement of your abdomen or an ultrasound.
  • Keep all your prenatal visits as told by your health care provider. It is important to follow your health care provider’s recommendations.

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