Vaginal bleeding does not occur during non-menstrual periods. If black blood appears during non-menstrual periods, it is definitely an abnormal condition with the following common causes: 1. Bleeding during menstruation is considered to be caused by ovulatory bleeding, which is relatively small and relatively bright red in color, if some components of the blood are special and may lead to a black color. If the bleeding during ovulation is small and does not last long, there is no need for special treatment. 2. Bleeding due to abnormal pregnancy, a urine pregnancy test should be performed first to rule out pregnancy. If the bleeding occurs in the pregnant state, it is considered to be caused by an abnormal pregnancy. Next, further ultrasonography should be performed to determine whether the bleeding is caused by an intrauterine pregnancy or an ectopic pregnancy.