Like many 10-year-old girls, Lindsay Kendrick likes to play sports and attend camp during the summer.
And like a growing number of girls her age, Lindsay also hit early puberty very early. Lindsay's mother, Beth, said her daughter first started menstruating when she was only 9.
"I thought it was going to happen early," said Beth. "She's been one of the tallest in her class, even taller than a lot of boys, and she started having early breast development."
Kendrick took Lindsay to her pediatrician, who told Beth that early puberty is much more common now, and said that Lindsay's period would probably start sometime in the next year.
"She started about two months after that," Beth said.
It's been a challenge for both Lindsay and Beth.
"She doesn't like talking to any of her friends about it," Beth said. "I try to keep up with her to make sure I send products with her to school."
A new study published in the journal Pediatrics may help lay the groundwork for future research that determines why, as past research has shown, more girls may be entering puberty early.
In the study, researchers assessed more than 1,200 6- to 8-year-old girls in three metropolitan areas for breast development and the appearance of pubic hair, both signs of early puberty. The research showed that by using these methods, scientists may be able to determine more accurately what factors could lead to early puberty in girls.
One of the study's authors told ABC News' Senior Health and Medical Editor Dr. Richard Besser, however, that determining early puberty was not the focus of the research.
"I don't think from this study we can say the age is going down in the world at large," said Mary Wolff, who is a professor of community and preventive medicine at Mount Sinai School of Medicine. "This study was not designed to look at if puberty was happening early or not."
The authors point out that the study does not use a nationally representative sample of subjects, and does not look at development over time to account for environmental exposure, dietary differences or other factors related to race and ethnicity. Additionally, some subjects were selected because they had existing risks for early puberty.
Another important element missing from this study is information about the onset of menstruation, which could indicate whether puberty has actually started.
"It's going to take a lot of follow-up to say whether this is really puberty," said Dr. Abby Hollander, associate professor of pediatrics at Washington University School of Medicine in St. Louis. "Within five years, we should be able to say whether the average age girls get their periods is earlier."
But pediatricians said past research suggests puberty may, indeed, be striking earlier than the 10-to 14-year-old age range that the National Institutes of Health set as the norm for girls.
"Ten percent of white girls at age 7 have breast development to some extreme, which is way younger than our original standard of evaluating normal versus abnormal," said Dr. Ann Budzak, a pediatrician with Gundersen Lutheran Health System in LaCrosse, Wisconsin.