Fetal hydrops is often serious and associated with a high perinatal motality rate. Cardiac causes of fetal hydrops include congenital heart diseases and rhythm disturbances. An irregular fetal heart rate may indicate atrial fibrillation and atrial flutter with variable AV conduction. Fetal atrial flutter is characterized by the pressence of flutter waves which are regular sawtooth undulations in the baseline that are larger than p waves. Authors experienced a case of fetal atrial flutter with hydrops fetalis at 30 week's gestation which was confirmed by fetal M-mode echocardiogram and electrocardiography. A new born infant had shown to have atrial flutter in utero and after delivery was successfully converted to normal sinus rhythm with digoxin and quinidene.