The prenatal diagnosis of Bartter syndrome can be based on the high chloride level in the amniotic fluid. Microscopic examination of the placenta in untreated cases showed extensive mineralization in the chorionic villi in previous studies. Two cases were presented at 26-29 weeks of gestation with severe polyhydramnios. The mothers were treated with Indomethacin, KCl, and serial amniocentesis in order to reduce the amniotic fluid volume and prevent fetal hypokalemia. The microscopic examination of the placenta revealed focal calcification and acute atherosis in placental vessels. The treatment with Indomethacin in the antenatal period can prevent severe nephrocalcinosis.