Twelve-year-old girls, genital development is a great individual differences, the development of early girls genital close to adult women, that is, the length of the uterus is about 7 to 8 centimeters, the uterus width of about 4 to 5 centimeters, the thickness of 2 to 3 centimeters; if this time the menstruation has not yet come may be slightly smaller than the above. Twelve-year-old girl’s reproductive organ development is a great individual differences, if the girl’s age of menarche is relatively early, may be to the age of twelve years old uterus size will be close to the adult, that is, the length of the uterus is about 7 to 8 centimeters, the uterus width of about 4 to 5 centimeters, the thickness of the 2 to 3 centimeters between. If the age of menarche is later, a slightly smaller uterus is also normal and physiological. Girls in puberty is the most important age of physical development, must pay attention to a reasonable diet, not picky about food and not partiality, and to ensure adequate sleep, to develop the habit of physical exercise. Develop some good habits, not only can improve the child’s physical quality, more conducive to promote the growth and development of children. Girls twelve years old should pay attention to vulvar hygiene, the development process if there is abnormal vaginal bleeding or lower abdominal pain need to go to the hospital in time.