The buildup of increased amniotic fluid, which surrounds a baby in the uterus during pregnancy.

Most of the time, polyhydramnios is mild. Various conditions can cause it. These include problems that affect the baby's digestive tract, central nervous system or certain other organs. Diabetes in the pregnant parent also can cause polyhydramnios.

Mild polyhydramnios often causes few or no symptoms. But serious forms of the condition may cause trouble breathing, swelling in the ankles or feet, or pain in the stomach area. It also can bring on feelings of tightness in the muscles of the uterus, called contractions.

Mild polyhydramnios rarely needs treatment. Other times, treatment for an underlying cause may help clear up the condition. If polyhydramnios is serious, a procedure to drain extra amniotic fluid and medicine taken by mouth may be needed.