It is not normal to have menstruation at the age of 9. Under normal circumstances, the age of women’s first menstruation is between 11-16 years old, 9 years old menstruation clinically belongs to the scope of precocious puberty, may be related to the misuse of drugs, eating too much food containing sex hormones or genetic factors. 1. Misuse of drugs: Misuse of drugs containing sex hormones, such as estradiol, progesterone, etc., which may stimulate the maturation of the sex organs, the age of menarche will be earlier, and the need to stop the drug in a timely manner. 2. Eating too much food containing sex hormones: Nowadays, most children like to eat fried chicken, snacks and other foods, which contain hormones that may stimulate the maturation of the sex organs of girls and advance the age of menarche. In general, eat less fried chicken, eat more fresh fruits and vegetables, enhance the exercise, and rest on time. 3. Genetic factors: Early menarche has a lot to do with genetic inheritance. If the age of menarche is early, it is recommended to go to the hospital in time for examination, such as bone age, sex hormone six, uterine ultrasound, ovarian ultrasound, etc., under the guidance of a professional doctor to clarify the cause of the disease and symptomatic treatment to reduce the adverse effects of the disease.