Polyhydramnios is too much fluid in the amniotic sac. The amniotic sac is the “water bag” inside the womb that protects your baby. Usually, there is about 1 liter of fluid by 36 weeks of pregnancy. Polyhydramnios is defined as a measurement, called the amniotic fluid index (AFI), of greater than 25 cm. About 2% of pregnant women have more than 25 cm and have polyhydramnios. Increased amniotic fluid can indicate a problem in the mother or the baby. It can also cause the following:

  • Early labor and delivery (preterm delivery)
  • Cesarean delivery
  • Increased bleeding after delivery
  • Reduced growth in the baby
  • Cord prolapse —The umbilical cord descends into the vagina before the baby.

Fetus in Utero, Amniotic Fluid
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About two-thirds of the time, the cause of polyhydramnios is unknown. One-third of the time, a cause is found. Some causes are related to the mother, and others are related to the baby.

Conditions that can cause polyhydramnios:

  • Birth defects in the fetus (anencephaly)
  • Rh disease (a treatable condition that occurs when mother and baby have different blood types)
  • Diabetes in the mother
  • Identical twins (twin-to-twin transfusion)