Intrauterine supraventricular tachycardia is an uncommon cardiac arrhythmia that presents difficult problems in diagnosis and management, especially in the very preterm infant. Serial ultrasound examinations were used to follow the course of fetal ascites and the maternal administration of digoxin to induce cardioversion. Higher maternal doses of digoxin than administered to the nonpregnant patient may be necessary to achieve adequate digitalization of the fetus. As many infants with supraventricular tachycardia require continued medical management, they should be delivered in a facility with neonatal intensive care capabilities.