Based on previous research showing differential age at onset of menarche by race/ethnicity,18 we defined early maturation as the onset of menarche 1 year before the average age at onset for each racial/ethnic group as reported in a recent national study,18 with cutoffs of 11.3 years for African American girls, 11.5 years for Hispanic and other girls, and 11.7 for non-Hispanic white girls.