Transvaginal color and pulsed Doppler sonography was performed on 106 singleton pregnant women; 75 had clinically normal pregnancies, and the remaining 31 patients had complicated pregnancies with vaginal bleeding. The gestational ages ranged from the 7th to 18th menstrual weeks. The aim of the study was to establish the earliest gestational age at which intracranial blood flow could be detected, in particular in the middle cerebral artery. The intracranial circulation becomes visible at the 8th week of gestation (7 weeks and 3 days). The end-diastolic component of blood flow is inconstantly present from the 11th to the 13th gestational week, and is always detected thereafter. A significant decrease in the pulsatility index (p < 0.05) and peripheral flow impedance index (p < 0.001) was observed during the early weeks of pregnancy in both the normal and complicated pregnancies. There was no significant difference between the groups (p > 0.05). Results suggest that Doppler studies of middle cerebral arteries in early pregnancy are unlikely to be of value in identifying fetal hemodynamic disorders in the early stages of spontaneous abortion.