It is normal for women of childbearing age to have a menstrual cycle of 21-35 days, with an average of 28 days, and once in a while it is normal to have an early or delayed period of 1 week. Most women have a menstrual cycle of about 30 days if they have a regular life and do not suffer from cold, fatigue, late nights, nervousness, endocrine disorders, etc. The menstrual cycle is influenced by the level of hormones secreted by the ovaries, and the length of the cycle is mainly related to the follicular growth period, which can fluctuate slightly. If the follicular growth period is long, a woman’s menstrual cycle will be prolonged, while if the follicular growth period is short, the menstrual cycle will be shortened accordingly. In order to keep the menstrual cycle normal, women need to pay attention to the regularity of work and rest, avoid cold and spicy stimulation, and appropriate activities to exercise the body.