This report describes a case of fetal supraventricular tachycardia (SVT) diagnosed at 12 weeks of gestation in a pregnant woman with diabetes mellitus. Transplacental digoxin therapy administered orally to the mother was unsuccessful. Subsequently, sotalol was added to digoxin to achieve fetal heart rate (HR) control and the conversion to sinus rhythm was achieved. The fetal HR remained stable until term, and a healthy male baby was born. The newborn electrocardiogram showed sinus rhythm with normal PR and QTc intervals. When the newborn was stable, he was discharged with propanolol. Sustained SVT is extremely rare during the first trimester. The goal of treatment in utero is the conversion to sinus rhythm or reduction of the ventricular rate to tolerable levels, preventing or even reversing fetal hydrops.