Using the Doppler technique, this study compared the prenatal and postnatal flow patterns of an infant with cerebral arteriovenous (AV) malformation. Fetal right ventricular end-diastolic dimension was 1.7 cm with right ventricular ejection equaling 66% of the combined cardiac output. Diastolic flow was reversed in the fetal aortic isthmus but forward-moving in the descending aorta, resulting in a watershed phenomenon. In the carotid arteries an increased forward diastolic flow was noted while the internal jugular vein exhibited a pulsatile arterial type of flow. The pulsatility index of the umbilical artery was normal. After birth and closure of the ductus arteriosus, the output from both ventricles was equally increased, and retrograde diastolic flow was then observed in the descending aorta. In conclusion, specific fetal features of cerebral AV malformation are increased right ventricular output probably related to the increased superior vena cava return, watershed phenomenon in the descending aorta causing the right ventricle to perfuse both the lower and upper body, and preserved umbilical circulation.