If a woman has black spots on her underwear, it is usually due to vaginal bleeding, which should be a small amount of vaginal bleeding. If the symptoms appear just after menstruation, it should also belong to the normal physiological phenomenon, because the menstrual period has just ended, there is still unclean menstrual blood inside the uterine cavity, which stays in the uterine cavity for a long time, and slowly flows out of the vagina, the color appears black, these are normal physiological phenomena. If there are black spots on the top of your underwear regularly, it may be vaginal bleeding caused by endocrine disorder, so you need to go to the gynecological department of the hospital and cooperate with the doctor for symptomatic treatment.