The symptoms of black slag menstruation in women may be caused by the following factors: 1. It may be caused by endocrine dysfunction, resulting in low menstrual flow, such as the decline of ovarian function, resulting in a decrease in the level of estrogen secretion, or due to insufficient luteal function in the body; 2. It may be caused by endometritis, adnexitis and other gynecological inflammatory diseases, which are usually accompanied by increased leucorrhea and soreness in the abdomen and lower back, in addition to the symptoms of black slag menstruation.