There are several reasons why women’s menstruation is blackish: 1, because of gynecological inflammation, such as vaginitis, pelvic inflammatory disease, endometritis, and tubal inflammation, etc. The most common ones are endometritis and vaginitis, because the formation of normal menstruation is formed by the regular contraction and contraction of the small arteries of the endometrium, and, at the same time, it needs to be discharged through the vagina. If there is inflammation in these two areas, it will lead to an increase in the permeability of the skin mucous membranes of the vagina or uterus, resulting in an obstruction of blood circulation, where the blood will stagnate, and the amount of hemoglobin in the stagnant blood will drop, aggravating the color of the blood, which can be dark red or even black. Part of the blood mixed into the menstrual blood, can lead to menstruation black. 2, for women with multiple sexual partners, to suspect whether there are sexually transmitted diseases, such as AIDS, syphilis, warts, etc. can also lead to menstruation black.