Auntie refers to menstruation. Having two periods in a month may be caused by ovulation, side effects of emergency contraceptive pills, gynecological diseases and other reasons, but it may also be a normal phenomenon. 1. Ovulation: When a woman is ovulating, due to fluctuations in hormone levels, the endometrium may shed a small amount, manifesting itself as a small amount of vaginal bleeding that lasts for 2 to 3 days and occurs about 14 days before the next menstrual period. 2. Side effects of emergency contraceptive pills: after taking emergency contraceptive pills, it will inhibit the endometrium of the female uterus, which may also cause a sudden increase in hormone levels in the body, and retreat bleeding occurs after its decline, which may lead to the situation of twice a month menstruation. 3. Gynecological diseases: some women suffer from uterine fibroids, endometrial polyps and other diseases, will not only lead to shorten the menstrual cycle, manifested in two menstrual periods in a month, may also have increased menstrual flow, menstrual period prolongation and other clinical manifestations. 4. Normal phenomenon: the normal menstrual cycle is 21~35 days, if some women’s menstrual cycle is 21~28 days, the situation of twice a month menstruation will occur. If you have two periods in a month, and if it is accompanied by other obvious discomforts, it is recommended to go to the hospital in time for ultrasound examination of the uterine adnexa and other programs to clarify the cause of the disease.