“As the name suggests, menstruation comes once a month, so why does it still “seem normal”? In the outpatient clinic, sometimes we will meet some depressed patients, obviously menstruation every month, why the first menstrual disorders, ultrasound said that the endometrium is uneven, the doctor let the diagnostic scraping, the results of a scraping out of the endometrial hyperplasia overgrowth. “Doctor, my period comes every month ah, how come?” . It all starts with what a normal period is. Normal menstruation is the regular cycle of endometrial shedding and bleeding that occurs in women of childbearing age and is regulated by cyclic ovulation of the ovaries. Usually, the menstrual cycle is 21-35 days, the menstrual period is about 5 days, and the bleeding volume of each menstrual period is about 5-80 ml. This is only the majority of cases, and there are quite a number of women of childbearing age who have their own menstruation pattern which is different from this one, some of them have their menstruation once every 2 months, and some of them have their menstruation once a year even. However, whether it is the majority or a minority of cases, the common characteristics of normal menstruation are: regular menstrual cycle: the interval between two menstrual periods is fixed; regular amount and duration of menstruation: the amount of each menstrual period is about the same, and it will not be more or less at one time. Therefore, if the menstrual cycle or the amount of menstruation is different from one’s own pattern, it cannot be regarded as a normal menstrual cycle. This kind of seemingly normal “menstruation” usually shows that the menstrual cycle is long and short, or that the menstrual cycle is still relatively regular, but the menstrual flow is sometimes heavy and sometimes light. There are many reasons for these seemingly normal “periods”, including ovarian dysfunction, endometriosis, fibroids, cervical lesions, and so on. None of these are normal, and if ignored, can lead to serious or even irreversible disease. Two common conditions are highlighted here. One is ectopic pregnancy. The patient has been menstruating on a normal schedule, but the last period was much less than usual, and then there was vaginal bleeding or pain in one side of the lower abdomen. If left untreated, the ectopic pregnancy may rupture and bleed, which is life-threatening. Another situation is polycystic ovary syndrome or endometrial hyperplasia, the patient’s menstrual cycle is long and short, sometimes once in half a month, sometimes not even once in two months, and the amount of menstruation is also irregular, sometimes more and sometimes less. In the long run, not only are they unable to have children, but also endometrial cancer may occur. In conclusion, normal menstruation is based on regular ovulation of the ovaries. Women of childbearing age who have normal menstruation have their own cycles, periods and menstrual flow patterns, and although they vary from one person to another, each person’s own patterns and characteristics are relatively regular and unchanged. Every woman should pay attention to her own menstrual situation, and once there is a difference from the usual menstrual pattern, it is recommended that she consult a doctor in time to prevent the problem before it occurs.