Aunt is menstruation, taking emergency contraceptive pills a week to menstruation, the color of brown, may be menstruation or endocrine disorders caused by early menstruation, but also may be vaginal bleeding, related to withdrawal bleeding, implantation bleeding, other gynecological diseases and so on. 1. Menstruation: a week after taking emergency contraceptive pills may be menstruation if it meets the time of menstruation. The first day of menstruation is small in volume, and it can be oxidized to brown color if it stays in the vagina for a long time. 2. Endocrine disorders: emergency contraceptive pills can cause endocrine disorders, resulting in menstrual irregularities, the phenomenon of early menstruation, the first day of menstrual blood can be brown. 3. Withdrawal bleeding: emergency contraceptive pills contain a large number of hormone components, which can cause changes in hormone levels, withdrawal bleeding occurs in about one week after stopping the pill, the color is brown. 4. Bleeding on implantation: Emergency contraceptive pills are not 100% successful in contraception, and there is a certain possibility of pregnancy. If the contraception fails and the embryo is implanted, some people may experience implantation bleeding after one week, usually with little bleeding and lighter blood color than menstrual blood, which may be brown. 5. Other gynecological diseases: Vaginal bleeding may be caused by cervicitis, cervical polyps, endometrial polyps and other gynecological diseases, which may be accompanied by abnormal leukorrhea, lower abdominal pain and other symptoms.