If there is brown blood on the top of the panties but no menstruation, women who have sex need to exclude pregnancy first, and the following reasons can cause this phenomenon: first, it is caused by ovulation bleeding, women are in the middle of two periods, after the follicle is mature and ovulation, estrogen will decline, resulting in the endometrium can not maintain growth, so the endometrium will cause local Second, uterine tumor and ovarian tumor can cause vaginal bleeding. Patients with uterine tumor will have irregular bleeding, which will lead to brown blood stains on the underwear; third, caused by cold during menstruation. After a period of time, the stagnant menstrual blood will be discharged; fourth, some gynecological inflammatory diseases may also cause brown discharge.