When a woman is ovulating and expels a dark, dirty substance, it is often considered to be a sign of ovulation bleeding. During ovulation estrogen fluctuates and falls, resulting in a small amount of endometrial shedding, which causes the vaginal bleeding manifestation. Since the amount of bleeding during ovulation is generally low, a small amount of bleeding will be sloughed off and oxidized in the vagina, and when it is discharged from the vagina, it will be seen as black or coffee-colored, which is actually a physiological manifestation. Ovulation bleeding occurs once in a while, usually do not need to do special treatment treatment, but if a woman is three consecutive months of ovulation bleeding, may need to take short-acting contraceptive pills for treatment.