Girls are Beginning Puberty at a Younger Age

The age at which girls begin puberty has fallen in the past two decades, and a new study shows this trend is continuing in some populations in the U.S. The study, “Pubertal Assessment Method and Baseline Characteristics in a Mixed Longitudinal Study of Girls,” published in the September 2010 issue of Pediatrics (published online Aug. 9), assessed the onset of puberty in more than 1,200 girls in three cities. Researchers found that 10.4 percent of white non-Hispanic girls had begun puberty at age 7, measured by breast development, compared to 23.4 percent of black girls and 14.9 percent of Hispanic girls. Among 8-year-olds, puberty had begun in 18.3 percent of white non-Hispanic girls, 42.9 percent of black girls and 30.9 percent of Hispanic girls. The numbers among white non-Hispanic girls represent a significant increase over rates seen in a 1997 study. What causes puberty to begin is thought to be a combination of genetics, environment and individual factors such as weight.