Normal menstruation has a cycle, not greater than 35 days and not less than 21 days, on average at 28 days, with a period of 3-7 days. If there is no pregnancy and no menstruation, there are several reasons, as follows: First, mental factors, because of touching something mental tension, anxiety. Second, environmental changes, from rural to urban, or abroad, overworked. Third, if there is obesity, underweight, malnutrition, can also cause no menstruation. Fourth, abnormal ovarian function, like polycystic ovary syndrome, obesity, ovarian function decline, hormone non-secretion, can also cause amenorrhea. Fifth, endometrial injury, due to repeated abortion scraping damage to the endometrium, so that the uterine cavity adhesions and amenorrhea. In short, such as future menstruation to look for the cause, timely hospital visits.