Doppler is a form of ultrasound which measures the speed of red blood cells moving along blood vessels. It takes two principal forms, one, where a colour map of the blood vessels is shown on the conventional ultrasound image (colour Doppler); another where a tracing of the flow is shown on a graph so that the speed of flow can be measured (spectral Doppler). You do not need a separate examination for Doppler; it is done at the same time as the usual ultrasound examination.

Why is Doppler useful?

Blood flow is important because it is the method by which oxygen is transported to body organs and therefore improves the function of these organs. We can measure blood flow to the uterus and to the ovaries. During a women's fertile years there is a fluctuation of blood flow during the menstrual cycle with more blood flow to the uterus in the second half of the cycle to aid implantation of the embryo. An increase in blood flow is also found before ovulation around healthy follicles which gives an indication of the health of the oocytes (eggs).

After the menopause blood flow to the uterus decreases due to the fall of oestrogen and when this occurs the effectiveness of hormone replacement therapy can be monitored by measuring the increase in blood flow.

Are there abnormalities in blood flow with specific conditions?

Yes, in polycystic ovary syndrome there is usually an increase in blood flow in the central part of the ovary (stroma) which reflects the local disturbance in growth hormones. Also the blood flow to the uterus is frequently poor which may explain the high miscarriage rate with this condition. With uterine fibroids there is usually an increase in blood flow and the higher the flow the greater the chance of fibroids growing. With ovarian cysts, a high internal flow indicates an increased risk of malignancy.