Uterine and ovarian artery blood flow

The increase in follicle numbers and size results in the rise of circulating oestrodiol (a form of oestrogen), whose main function is to develop the endometrium in preparation to receive a fertilized ovum a few days after ovulation. The endometrium should be at least 7mm thick in order to enable a viable pregnancy, and ideally 10-15mm thick. The oestradiol is transported from the ovaries, via the uterine arteries, to the endometrial tissue to carry out this proliferation of the endometrium. Increased blood flow and decreased velocity are likely to both increase the amount of oestradiol supplied to the uterus and therefore thickness and quality of the endometrium.

In the luteal phase of the menstrual cycle, ovarian arterial blood supply is needed to nourish the highly vascular corpus luteum and the venous blood return is required to enable the transport of progesterone from the corpus luteum to the uterus to enhance the secretory endometrium and maintain early pregnancy until the placenta establishes itself and takes over progesterone production.

Successful IVF and embryo transfer require optimal endometrial receptivity at the time of implantation. Blood flow impedance in the uterine arteries is measured as the pulsatility index, or the PI. This can be used to assess endometrial receptivity during IVF. An optimal range of PI at the time of embryo transfer, is between 2.0 and 2.9. A study was carried out to evaluate the effectiveness of electro-acupuncture treatment on reducing high blood flow impedance in the uterine arteries to an optimal PI level between 2.0 and 2.9. Ten infertile women, aged between 25 and 40, with a mean PI of more than 3.0 in the uterine arteries were given electro-acupuncture treatments twice a week for 4 weeks. The PI measurements reduced significantly when tested straight after the 8 treatments, and they remained low when re-tested 10-14 days later.

This and other studies have concluded that both acupuncture and Chinese herbal medicine enhance the flow of blood in the uterus and should therefore promote the chances of conception.