a period is a release of blood from a girls uterus, out through her vagina. It is a sign that she is getting close to the end of puberty. heavy periods in teen girls are often brushed off as a normal part of adolescence. But its not normal, and it can indicate a more serious condition. Discover how the young womens blood disorders program offers proper diagnosis and treatment to prevent long-term complications. Your teen may also require a few additional tests and consultations to confirm or exclude the diagnosis of possible underlying causes. Treatment depends on the cause of amenorrhea and its severity. Teens who experience them might avoid activities like swimming or biking with friends. According to kidshealth, most girls get their first period between the ages of 10 and 15, but the number of days between periods, as well as the number of days your daughter bleeds, can vary much more significantly 3. While many doctors refer to the average 28-day cycle, that isnt always the magic number for teen girls.