Antenatal Bartter syndrome: a rare cause of unexplained severe polyhydramnios

A woman presented with polyhydramnios at 22 weeks of gestation with a structurally normal fetus and placenta. Biochemical analysis of amniotic fluid detected a very high level of chloride (582 mmol/L), which led to the diagnosis of Bartter syndrome. With serial amniocentesis and indomethacin therapy, the pregnancy continued to 36 weeks. Neonatal and subsequent investigations further supported the diagnosis of Bartter syndrome. The infant was well at birth and now, at 5 months of age, is gaining weight normally on indomethacin.