They may come to their physical exams a little self-conscious. Their mothers, though, can be more than a little concerned.
Some young girls, barely into grade school, are showing the first signs of puberty. A study published in the journal Pediatrics finds that these early maturers are far more common now than just a decade ago.
By age 7, about 10 percent of white and 23 percent of black girls had started developing breasts, the researchers found. That compared to just 5 percent and 15 percent respectively in a similar study published in 1997.
The new research confirms what many doctors have been seeing in their practices for years, said Lore Nelson, an adolescent medicine specialist at the University of Kansas Hospital.
“It’s one of those things everyone thought was happening, now it looks like it really is happening,” she said. “We’re just seeing girls maturing earlier.”
The researchers suggest the epidemic of childhood obesity — one in five U.S. children ages 6 to 11 — may be a cause of girls’ precocious development.
Obesity has been associated with early puberty because fat cells can trigger the production of the female hormone estrogen. The researchers did find that breast development at age 7 was more common among heavier girls. But more than obesity may be at play. Certain chemicals in the environment also need to be studied, many say.
These chemicals, such as bisphenol A, act like estrogen. Bisphenol A is used in many plastics, food packaging and even dental sealants.
Whatever the cause, Nelson said, “it would behoove everyone to diet and exercise. Obesity is such a problem now for kids.”
But early maturation itself can cause serious health and social problem for young girls.
Girls who enter puberty early run higher risks of breast cancer and endometrial cancer.
They are more likely to have lower self-esteem and a poor body image. Their rates of eating disorders, depression and suicide attempts are higher. They’re more likely to become sexually active at an early age.
The federally funded study recruited 1,239 girls ages 6 to 8 from East Harlem in New York, the Cincinnati metropolitan area and the San Francisco Bay area. The researchers examined the girls at ages 7 and 8 for early signs of puberty.
The study did not look at when girls first menstruate, which usually begins at about age 12 or 13.