Early menstruation may be due to pathological reasons or normal physiological phenomena. 1. Pathological causes (1) Luteal insufficiency: due to environmental factors, emotions, diet, etc., it may disturb the endocrine system, resulting in endocrine disorders leading to luteal insufficiency, which will make the corpus luteum atrophy in advance, and the phenomenon of early menstruation will occur. (2) Uterine fibroids: after suffering from uterine fibroids, especially submucous fibroids and interstitial fibroids, it may affect the menstrual cycle, shorten the menstrual cycle, lengthen the menstrual period and increase the menstrual flow. (3) Endometriosis: endometriosis such as endometritis, atypical hyperplasia of the endometrium, endometrial cancer, etc., may also lead to early menstruation. 2. Physiological reasons If a woman’s menstrual cycle is 28 days and every month has 30 or 31 days, causing the illusion of early menstruation, this is a normal phenomenon if calculated according to the menstrual cycle. There are relatively more reasons for early menstruation, but the specific reasons need to be clarified after the woman goes to the hospital and undergoes the relevant program.