Several studies have documented earlier onset of puberty in girls
over the past few decades. In a longitudinal study following more than 1,200 girls for seven years, researchers found those with higher BMI had earlier onset of puberty, as measured by breast development
, and that white girls are entering puberty at younger ages than previously reported.
The age at onset of breast development varied by race, BMI
, and geographic location. In white, non-Hispanic girls, breast development began at a median age of 9.7 years, which is earlier than previously documented, according to the study authors. Black girls continue to experience breast development earlier than white girls, at a median age of 8.8 years, compared to 9.3 years for Hispanic girls and 9.7 years for Asian girls. However, BMI was a stronger predictor of puberty onset than race or ethnicity.
Editor’s Note: This issue of Pediatrics includes a related commentary, “The Enigmatic Pursuit of Puberty in Girls,” which will also be published online Nov. 4.