Transvaginal colour flow imaging of the uterine arteries during the ovarian and menstrual cycles

Uterine arterial blood flow was studied at defined times during the ovarian or menstrual cycles. Transvaginal colour pulsed ultrasound was used to identify the vessels in 23 healthy women. Blood flow impedance as reflected by the pulsatility index (PI) was determined for both arteries on 132 occasions. There was no significant difference in the PI values between the right and left arteries. The average PI value was used for subsequent analysis (range 0.5-5.6; mean 2.8). Peak mean PI values occurred on day 1 of menses (4.6), the day of the plasma oestradiol peak (3.7) and the day of the LH peak plus 3 (2.9). The lowest mean PI values (indicating the least impedance to blood flow) occurred on the day of the LH peak minus 6 (2.6), and the day of the LH peak plus 9 (1.9). There are complex temporal relationships between uterine blood flow, ovarian morphology, the concentrations of plasma oestradiol and progesterone and the thickness of the endometrium.