A woman’s menstrual blood is not always red or dark red at the time of menstruation. Brown menstruation, which is relatively dark in color, may occur just after menstruation or near the end of menstruation. Brown menstruation is also a normal menstruation, but the color is caused by oxidation. In fact, as long as a woman’s menstrual flow is normal, either brown, dark red or bright red menstrual blood is a normal manifestation and can be left untreated. If the entire menstrual period is brown, and the menstrual volume is particularly small and long-lasting, it is an abnormal manifestation and should be considered as anovulatory gonorrhea caused by the ovaries not ovulating. For women with normal menstrual flow and color, the sudden appearance of brown blood with significantly less volume than usual may be caused by an unplanned pregnancy, such as ectopic pregnancy or pre-eclampsia.