To evaluate the umbilical venous blood flow during labor, 11 normal pregnant women were selected and were divided into two groups. Group 1: spontaneous delivery (n=6) and Group 2: PGF2α induction (n=5). Color flow mapping 2-D Doppler echocardiography was used. Umbilical venous blood flow velocity was measured by FFT pulsed Doppler spectral analysis with an angular correction by color flow image. 2-D Doppler examinations were performed before the onset of pains, during pains at 10 minutes interval and within 5 (3 to 5) minutes interval. The umbilical venous diameter did not change through labor. In Group 1, the umbilical arterial and venous blood flow velocities were 55.6±7.7 cm/sec and 18.5±1.0 cm/sec before the onset of labor. These values did not change at 10 minutes interval of labor (55.5±7.1; 18.2±1.1), but significant decrements were observed within 5 minutes interval of labor (45.5±2.1; 15.8±1.1). In Group 2, almost same tendency was observed. These results demonstrated that the umbilical blood flow significantly reduced as the labor progressed. It is suggested that the reduction of umbilical blood flow during labor may be related to the intensity of pains.