Teen Athletes and Irregular Menstruation

Menstrual Cycles

• All girls develop differently, but most girls start having periods between the age of 9 and 15, according to the Boston Children's Hospital website. A girl's breasts usually develop two to three years before her periods start. Genetics can influence the start of menstruation in some families -- it is common for girls to start earlier or later than average. A typical menstrual cycle is 28 days long, or approximately once a month, but may vary anywhere from 21 to 45 days. Most periods last three to seven days.

Irregular Periods

• Teenagers may have irregular periods for the first year or two after menstruation begins, although some girls take longer to develop regular periods, according to the Boston Children's Hospital site. The amount of menstrual flow and the length of the period may also vary in the first few years. It is unusual for a teen to start having periods and then have no periods -- a condition called amenorrhea -- for an extended period of time. If amenorrhea occurs after a teen has begun menstruating, it may be a sign of a medical problem.

Exercise and Menstruation

• Teens who exercise intensively sometimes also try to lose weight, thinking that will improve their athletic performance, according to the Kids Health website. A teen who exercises too much and doesn't eat properly, however, can have insufficient estrogen, which is one of the hormones that regulates menstrual periods. As a result of these lower estrogen levels, a teen may have irregular periods or even develop amenorrhea. Teen girls who begin training intensively before menstruation starts may not have periods at all.

Other Issues

• In addition to excessive athletic activity, teens can have menstrual irregularities as a result of thyroid or hormonal problems, low body fat or other health issues. Teens should be taught to track their menstrual cycles in order to recognize possible problems with menstruation, according to the American Academy of Pediatrics. If your daughter has not started her period within three years after her breasts begin to develop, is 15 and has not yet started her periods, or has very irregular periods, consult your family doctor or pediatrician.