The present study was designed to evaluate the changes of uterine blood flow changes during pregnancy in Wistar rats. Also, to investigate the clinical applicability of noninvasive color Doppler ultrasound to charactrize the uterine blood flow indices in the maternal uterine arteries in rats. Ten female rats weighing 280-300 gm were used and the Doppler indices were blood flow volume (BFV), time averaged maximum velocity (TAMV), peak systolic velocity (PSV), resistance index (RI), pulsatility index (PI), and diameter (D) of uterine arteries in rats during pregnancy. Examination of the uterine arteries started three days after breeding and continued at days 7, 14 and 18. Based on the noninvasive color doppler sonography, the BFV, TAMV, PSV were increased significantly at all-time points of the examination. On the contrary, the RI and PI decreased steadily at all-time points. The RI and PI showed a significant increase at day 20 of gestation. Altogether, these results indicate that non-invasive Doppler ultrasound parameters provide important information toward understanding changes in the vasculature and its perfusion of the uterus during the pregnancy period in rats. Furthermore, the present results would be key values for the uterine blood flow during pregnancy in Wistar rats.