The normal color of menstruation is dark red, then the majority of women’s menstrual flow is between 35-58ml, which is normal. If it is less than 20ml, then clinically it can be diagnosed as low menstrual flow. If the color of menstruation is light and the amount is low, then clinically it may be due to the following reasons, the first is because of chronic inflammation of the uterine lining. When there is chronic inflammation, it will lead to an increase in local exudation, so that when the menstrual period just comes, then it will make the menstrual blood dilute and appear lighter in color. Rather, low menstrual flow is often caused by a relatively thin endometrium, such as the decline in estradiol caused by the decline in ovarian function, so the endometrium is thin, which leads to low menstrual flow. In addition, polycystic ovary syndrome may also be clinically associated with low menstrual flow. So in this case, it is recommended to have an ultrasound to find out the condition of the endometrium, and if necessary, a diagnostic scraping can be done to rule out the possibility of endometrial inflammation. In addition, ultrasound can also be used to find out whether there are polycystic changes in both ovaries.