Clinically common decrease in menstrual flow may be caused by the following reasons: 1. The decrease in menstrual flow is caused by a malfunction in ovulation. Originally, there is ovulation every month, but as a result, there is no ovulation this month. If there is no peak of estrogen in the body and no stimulation of endometrial proliferation, it will lead to reduced menstrual flow; 2. The source of menstruation is the endometrium, and thinning of the endometrium can lead to reduced menstrual flow; 3. Pathological factors such as endometrial adhesions and damaged endometrium can lead to reduced menstrual flow. If estrogen comes over again, even though there is ovulation, the endometrium cannot proliferate due to damaged or uterine adhesions and other factors, which may also show as a significant decrease in menstrual flow. If it is found that the menstrual volume is significantly reduced compared to the past, the patient should go to the hospital as much as possible to find a doctor to make identification and clarify the cause of the reduced menstrual volume. 4. Some women may have reduced menstrual volume due to mental factors only, which may be ignored and can be adjusted over after a period of time.