We discovered supraventricular tachycardia with advanced hydrops in the setting of normal cardiac anatomy at 26 weeks of gestation which resolved successfully following administration of digoxin and flecainide to the mother. A female baby was born after a premature rupture of the membranes at 30.6 weeks. The neonate was in sinus rhythm, showed a progressive regression of right ventricular insufficiency, but developed signs of acquired pulmonary valvar and subvalvar stenosis at 2 months of age.