polyhydramnios birth defects
Causes of polyhydramnios. 1  Polyhydramnios can sometimes mean that there is a birth defect or a medical problem. 2  Birth defects that affect the baby's ability to swallow and process amniotic fluid may cause polyhydramnios. Most of these birth defects are rare, but it is important to perform a detailed ultrasound to make sure there is no evidence of these conditions.