Causes of polyhydramnios include the following: Fetal malformations (eg, gastrointestinal or urinary tract obstruction) Multiple gestation Maternal diabetes Fetal anemia, including hemolytic anemia due to Rh incompatibility Other fetal disorders (eg, infections) or genetic abnormalities Idiopathic Complications With polyhydramnios, risk of the following complications is increased: Preterm contractions and possibly preterm labor Premature rupture of membranes, sometimes followed by placental abruption Fetal malposition Maternal respiratory compromise Umbilical cord prolapse Uterine atony Postpartum hemorrhage Fetal death (risk is increased even when polyhydramnios is idiopathic) Risk of complications tends to be proportional to the degree of fluid accumulation and vary with the cause.