There are several reasons for dark brown vaginal discharge: First, it may be due to gynecological inflammation, such as endometritis, pelvic inflammatory disease, tubal inflammation and vaginitis, especially vaginitis, which may cause abnormal vaginal discharge. This is because the vascular permeability of the vaginal skin and mucous membrane will change when there is inflammation in the vagina, especially the capillary permeability will expand, resulting in inflammatory exudate flowing out through the vagina, thus producing dark brown discharge visible to the naked eye. Second, if the woman is older, consider tumor diseases, such as cervical tumor, endometrial tumor, mucus tumor of the uterus. It can also be a pelvic tumor. The material produced by the tumor or the material formed by necrosis or shedding, as well as the erosion or ulcer caused in the growth area, can cause abnormal vaginal discharge, and the discharge produced can be blackish-brown.