Once your daughter’s menstrual cycle becomes more regular, she should expect to have a period every 25 to 30 days. However, it’s not uncommon for girls to have periods as frequently as every 21 days, or as spread out as every 45 days.
The time lapse between periods is highly dependent upon genetics, stress, and weight. You should also know that there are many documented cases where girls have essentially stopped having periods during times of grueling physical exertion, such as long-term training to run in marathons, or if they are anorexic. The American College of Obstetricians and Gynecologists recommends that adolescent females seek a medical evaluation if they have irregular menstrual cycles that occur less than every 90 days.
