12-year-old girl menstruation delay, if there is no special discomfort symptoms, can not be treated for the time being, you can give observation. Because 12-year-old girls, the pituitary axis development is not particularly mature, before the irregular menstrual cycle, can play a role in growth and development, can grow again. If the menstrual cycle is regular, the chances of growing longer are lower. If a 12 year old girl is low and has delayed menstruation, she can be left untreated for the time being to grow in her natural state. If the girl has dribbling menstruation or abdominal pain is more serious, it is recommended to go to the hospital for ultrasound examination, according to the results of the examination, to give effective treatment.