After a girl grows pubic hair, she will menstruate in about two to three years, but the exact time is difficult to determine as each person’s situation is different. Girls will enter puberty around the age of 10-11. Under the action of gonadotropins, the ovaries will grow and will secrete estrogen, and the secondary sexual characteristics will gradually develop, starting breast development, growth of pubic hair, armpit hair and so on. After the growth of pubic hair, it takes about two to three years, i.e. around the age of 13-14, to have the first menstrual period. However, due to the differences in each girl’s growing environment, nutritional status and heredity, girls who develop earlier may have their menstruation at the age of 11, while some girls who develop later due to malnutrition may have their first menstruation after the age of 14. However, as long as they do not exceed the age of 16, it can be regarded as a normal range. Thus, girls will menstruate around two to three years after growing pubic hair under the influence of estrogen and progesterone.