The normal menstrual cycle for women is 21-35 days, with an average of 28 days. According to the cyclic changes of the endometrium, it is divided into a menstrual phase of about 1-4 days, a proliferative phase of about 5-14 days, and a secretory phase of about 15-28 days. The menstrual cycle is calculated as one menstrual cycle starting from the first day of the onset of menstruation to the first day of the next menstruation. The normal menstrual cycle is 21-35 days, with an average of 28 days. The length of the menstrual cycle varies from person to person and can be early or late due to environmental influences. If it does not exceed 7 days, it is considered normal. The average woman begins to experience menarche at the age of 13-14 and menopause begins at 45-55. The menstrual cycle usually consists of 3 phases: the menstrual phase corresponds to days 1-4 of the menstrual cycle, the proliferative phase corresponds to days 5-14 of the menstrual cycle, and the secretory phase corresponds to days 15-28 of the menstrual cycle. A long or short menstrual cycle indicates a possible endocrine disorder or organic pathology in women, such as a shortened menstrual cycle, which can be caused by submucosal fibroids or luteal insufficiency.