A girl's weight and race, as well as other genetic factors, can cause early menstrual cycles. According to the U.S. Centers for Disease Control and Prevention, the average age of menarche, or first menstrual period, for American girls is 12.6. Menstruation normally begins about two years after a girl first begins to develop breasts, but a girl can have her first period at any point between age 8 and 15 years old. Girls experiencing menarche earlier than age 8 or after age 15 should be evaluated by an endocrinologist.
Race and Socioeconomic Factors
According to the CDC, about 2.9 percent of white, non-Hispanic girls experience menarche earlier than age 10. For African-American girls, the rate is 5.1 percent. As of 2010, scientists have not identified a reason for the racial disparity, but in the July 2009 issue of "Cancer Causes and Control," Dr. Dejana Braithwaite noted a correlation between high household income and early menarche among African-American girls. For white girls, the opposite was true.
Weight
A high body mass index may correspond to early menarche. In the April 2003 issue of "Pediatrics," Sarah Anderson, a researcher at Tufts University in Boston, Massachusetts, wrote that high body weight was strongly associated with early menarche, even after controlling for race. Anderson also observed that the average age of menarche for American girls fell as childhood obesity rates rose.
Genetics
If her mother experienced an early menstrual cycle, it is likely that a girl will also experience an early menstrual cycle. In the October 2008 issue of "Cancer Epidemiology, Biomarkers and Prevention," Dr. Lisa Colbert wrote that the level of activity of a girl's mother during pregnancy also influenced menarche. The less physically active a mother is during pregnancy, the lower her daughter's age at menarche.
References
- Centers for Disease Control and Prevention: Menarche
- U.S. Department of Health and Human Services: Women's Health
- Centers for Disease Control and Prevention: Fertility, Family Planning and Reproductive Health
- "Cancer Causes and Control"; Socioeconomic Status in Relation to Early Menarche Among Black and White Girls; Dejana Braithwaite, Ph.D.; July 2009
- "Pediatrics"; Relative Weight and Race Influence Average Age at Menarche; Sarah E. Anderson, M.S.; April 2003
