When a child is just born, gonadal hormone levels are usually high and estrogen values are on the high side, so breast development may occur, usually most noticeable around one year of age, and this should be a normal physiological phenomenon. As the child’s sex hormones gradually decline, the breasts slowly shrink and return to normal at about two weeks of age. If the child’s breasts continue to increase in size and are accompanied by other symptoms, such as pubic hair and a significant increase in height, the child should consider the possibility of precocious puberty and go to the hospital for gonadal hormone level measurement, ovarian ultrasound, pituitary gland MRI, and even a bone age check. If gonadal activation is determined, the child will be given medication to suppress gonadal activation in order to achieve normal height. True precocious puberty can affect the child’s height and have an impact on the child’s overall development.