Blood velocities in the uterine artery in humans during labour.

Blood velocities in the uterine arteries were measured during labour in humans, by means of the pulsed ultrasound Doppler velocity meter (UNIDOP). The uterine arteries were approached through the abdominal wall at the lateral border of the uterus and through the lateral vaginal fornix. At a depth of 0.5-1.5 cm from the lateral vaginal fornix there were three different arteries in each woman. One of these arteries had similar velocity spectra to the uterine artery as measured through the abdominal wall higher up along the uterus, and the velocities were in the same range. The mean velocities were high and the velocities in diastole were high compared to those in systole. During uterine contractions the velocities were reduced during diastole, reducing mean velocities by 20-40% as measured through the vagina and by 50-60% when measured higher up through the abdominal wall. A second artery, which we believe is a branch of the uterine artery traversing the myometrium, had lower mean velocities and a greater difference between systole and diastole. During contractions the velocities were reduced by 100%. A third artery, which we believe is the descending branch of the uterine artery, supplying the cervix and vagina, had the lowest mean velocities, with backflow during diastole. During contractions the velocities increased 100-140%.