Intermenstrual bleeding refers to periodic uterine bleeding during ovulation. It does not necessarily occur every time during menstruation. Usually uterine bleeding during ovulation is not profuse and tends to be overlooked. The bleeding usually occurs 12-16 days in the menstrual cycle, lasting about 2-7 days and generally stopping automatically. The accompanied symptoms is light lumbar or abdominal pain in one side, known as pain during ovulation. It occurs in a time between two menstruations. This period is marked by emptiness of the uterus after discharge of menses, deficiency of the thoroughfare and conception vessels, gradual accumulation of menstrual blood from emptiness to abundance. The period between two menstruations is marked by the development from deficiency to exuberance, exuberance of yin-essence, internal activation of yang-qi and ovulation. If the regulatory function of yin and yang is normal, the body can adapt to such physiological changes.