If you find that your underwear is brown the day after intercourse, this is because there was bleeding at the time of intercourse. The bleeding is not discharged from the vagina in time, it accumulates in the vagina and turns brown when it is discharged from the vagina, which is also known as contact bleeding in the clinic. The reason why contact bleeding occurs, in the clinical common cervical inflammation, vaginal inflammation and cervical cancer, as well as the uterine submucosal fibroids have the situation will also lead to coital bleeding. Therefore, it is recommended to do gynecological examination to understand the local conditions of the vulva, vagina and cervix. If there is a fatty organism, it is recommended to take it out and do pathological tests, and it is clinically recommended to do cervical cancer screening to find out whether there is cancer or pre-cancerous lesions of the cervix, which need to be dealt with promptly in the clinic. If there are submucosal fibroids, it is recommended to perform hysteroscopy to remove the submucosal fibroids.