Aunt usually stands in for menstruation, and girls usually menstruate between the ages of 11 and 16. A girl’s first period, also known as menarche, is an important sign of puberty. The timing of the first menstruation is different for every girl and is mainly influenced by genetic factors, nutrition and other aspects. Most girls menstruate between the ages of 11 and 16. Some may have it earlier, before the age of 11, and some girls may have it later, over the age of 16. Girls do not establish a regular menstrual cycle immediately after menstruation. Because the central positive feedback mechanism for estrogen has not matured at this time, the menstrual cycle is often irregular, and it takes 5-7 years for some girls to establish a regular cycle of ovulation before menstruation becomes normal. If a girl has her period before the age of 8 or if she has not had her period beyond the age of 18, it is necessary to consult a doctor in time for examination, clarification of the cause of the disease, and specific treatment.