Researchers found that about 10 percent of 7-year-old Caucasian girls were developing breasts, compared to 5 percent more than 10 years ago.
African-American girls hit puberty at a higher rate. Researchers saw early maturation in 24 percent of 7-year-old black girls. That also reflected an increase from previous studies.
About 15 percent of Hispanic girls in the study hit puberty at age 7.
The numbers jumped for 8 year old girls. 18 percent of 8 year old Causasian girls studied had developed breasts compared to 43 percent of black girls and 31 percent of Hispanics.
Doctors believe weight gain and obesity can help trigger early puberty. There are environmental and genetic factors that could be contributing as well.
The results were published online by the journal Pediatrics.
For more information: http://pediatrics.aappublications.org/cgi/content/abstract/peds.2009-3079v1