The bleeding time of a girl’s first menstrual period is not particularly regular, but most will end in 3-7 days of bleeding. Because the first menstruation in girls, the normal time of menarche should be between 11 and 16 years old. At this time, the uterus itself is not fully developed, so it may be normal for the bleeding time to vary because the physiological functions are not particularly well developed. As long as a girl is able to have her first menstrual period normally between the ages of 11 and 16, it will reflect that there are no major abnormalities in the uterus. If the first menstruation does not occur beyond this age, the development of the uterus needs to be checked by ultrasound. If the uterus does not develop beyond this age, it is necessary to go to the hospital to check the development of the uterus through ultrasound to see if there is a congenital abnormality, and then to treat the symptoms early.