Polyhydramnios is when you have too much amniotic fluid. Amniotic fluid is the fluid that surrounds your baby in your uterus (womb). It’s very important for your baby’s development.

How do you know if you have polyhydramnios?

Many women with polyhydramnios don’t have symptoms. If you have a lot of extra amniotic fluid you may have belly pain and trouble breathing. This is because the uterus presses on your organs and lungs.

Your health care provider uses ultrasound to measure the amount of amniotic fluid. There are two ways to measure the fluid: amniotic fluid index (AFI) and maximum vertical pocket (MPV).

The AFI checks how deep the amniotic fluid is in four areas of your uterus. These amounts are then added up. If your AFI is more than 24 centimeters, you have polyhydramnios.

The MPV measures the deepest area of your uterus to check the amniotic fluid level. If your MPV is more than 8 centimeters, you have polyhydramnios.

Ask your provider if you have questions about these measurements.

What problems can polyhydramnios cause?

Polyhydramnios may increase the risk of these problems during pregnancy:

  • Premature birth – Birth before 37 weeks of pregnancy
  • Premature rupture of the membranes (PROM) – When the amniotic sac breaks after 37 weeks of pregnancy but before labor starts
  • Placental abruption – When the placenta partially or completely peels away from the wall of the uterus before birth
  • Stillbirth – When a baby dies in the womb after 20 weeks of pregnancy
  • Postpartum hemorrhage – Severe bleeding after birth
  • Fetal malposition – When a baby is not in a head-down position and may need to be born by cesarean section

What causes polyhydramnios?

In about half of cases, we don’t know what causes polyhydramnios. In other cases, we can identify a cause. Some known causes are:

  • Birth defects, especially those that affect the baby’s swallowing. A baby’s swallowing keeps the fluid in the womb at a steady level.
  • Diabetes – Having too much sugar in your blood
  • Mismatch between your blood and your baby’s blood, such as Rh and Kell diseases
  • Twin-to-twin transfusion syndrome (TTTS) – If you’re carrying identical twins, this is when one twin gets too much blood flow and the other gets too little.
  • Problems with the baby’s heart rate
  • An infection in the baby

How is polyhydramnios treated?

When an ultrasound shows you have too much amniotic fluid, your provider does a more detailed ultrasound to check for birth defects and TTTS.

Your provider also may recommend a blood test for diabetes and an amniocentesis. Amniocentesis is a test that takes some amniotic fluid from around the baby to check for problems, like birth defects.

In many cases, slight polyhydramnios goes away by itself. Other times, it may go away when the problem causing it is fixed. For example, if your baby’s heart rate is causing the problem, sometimes your provider can give you medicine to fix it.

If you have polyhydramnios, you usually have ultrasounds weekly or more often to check amniotic fluid levels. You may also have tests to check your baby’s health.

Having too much amniotic fluid may make you uncomfortable. Your provider may give you medicine called indomethacin. This medicine helps lower the amount of urine that your baby makes, so it lowers the amount of amniotic fluid. Amniocentesis also can remove extra fluid.

If you have slight polyhydramnios near the end of your pregnancy but tests show that you and your baby are healthy, you usually don’t need any treatment.

Is polyhydramnios common?

About 1 out of 100 (1 percent) pregnant women have too much amniotic fluid. It usually happens when fluid builds up slowly in the second half of pregnancy. In a small number of women, fluid builds up quickly. This can happen as early as 16 weeks of pregnancy, and it usually causes very early birth.

Last reviewed: June, 2013