The main reasons for brown vaginal discharge are as follows: 1. Ovulatory bleeding, which occurs about a week after the end of menstruation, when the body’s estrogen level changes greatly after ovulation, the endometrium sheds, and there is brown discharge or a small amount of blood. 2. Gynecological inflammation, when suffering from vaginitis, the mucous membrane of the vagina becomes congested and edematous, accompanied by discharge. 3. If you have endometritis or polyps in the uterus, you will also discharge brown discharge and blood, accompanied by pain in the lower back and abdomen. 3. IUD stimulation, when the body is in the process of adapting to the IUD, the endometrium is stimulated by the IUD and is discharged. 4. The use of certain drugs, such as short-acting contraceptives, can also cause irregular vaginal bleeding.