Causes

Some of the known causes of polyhydramnios include:

• A birth defect that affects the baby's gastrointestinal tract or central nervous system
• Maternal diabetes
• Twin-twin transfusion — a possible complication of identical twin pregnancies in which one twin receives too much blood and the other too little
• A lack of red blood cells in the baby (fetal anemia)
• Blood incompatibilities between mother and baby
• Infection during pregnancy

Often, however, the cause of polyhydramnios isn't clear.