Premature menstruation for 9 days is most likely due to the following reasons: 1. submucosal fibroids. submucosal fibroids, due to growth into the uterine cavity, cause a relative increase in the area of the uterine cavity and poor contraction of the uterus, leading to early menstruation, resulting in a shortened menstrual cycle, and the amount of menstruation will increase and irregular vaginal bleeding will occur. 2. inflammation of the endometrium. long-term inflammation of the endometrium causes brittle endometrial tissue, so that 3. endocrine disorders, such as luteal insufficiency, under normal circumstances, the corpus luteum is maintained for about 12 days. However, when the corpus luteum is insufficient, the maintenance time is shorter and vaginal bleeding will occur after the corpus luteum retreats, which means early menstruation. Therefore, when menstruation is early, a detailed examination must be done to find out the cause before giving treatment.