The average age of menarche for girls is around 12 years old, with some early to around 10 years old and some later to around 18 years old, with large individual differences. However, if a girl has menstruation before the age of 10, she should be considered precocious; if she still does not have menstruation over the age of 18, she needs to go to the hospital for gynecological ultrasound and hormone six tests. Since puberty, female ovarian function and reproductive system gradually develop. When menstruation begins, most menstrual cycles are irregular and menstrual volume is small because ovarian function is not fully developed. However, as the body continues to develop, the ovarian function gradually develops and matures, ovulation begins to occur, and the menstrual cycle gradually becomes normal, so the regularity of menstruation marks the maturity of the female reproductive system. During menstruation, women need to take rest and avoid strenuous exercise, and pay attention to abdominal warmth and menstrual hygiene. If menstruation is still irregular after 2 years, you should visit a gynecologist for examination.