(HealthDay)—It's rare for children in the United States aged 10 to 12 to be sexually active, especially on a voluntary basis, a new study finds. However, almost one in five teens has had sex before age 15, and 16,000 girls under 15 get pregnant each year.
The researchers launched the study after the debate heated up over access to Plan B, the so-called "morning after" birth control pill. It can be used to prevent pregnancy up to 72 hours after sex.
Opponents contend the emergency contraceptive pill causes abortions, but medical experts say that's inaccurate. In the United States, customers must be at least 17 to buy emergency contraceptive pills over the counter, and President Barack Obama made comments in 2011 supporting the move by saying 10- and 11-year-olds shouldn't have access to it "alongside bubble gum or batteries."
The new study finds that "sex and pregnancy are quite rare among the youngest adolescents, which may be different than the perceptions of many people," said co-author Lawrence Finer, director of domestic research at the Guttmacher Institute, which supports access to sexual education and contraception. "There was never a time when a very large percentage of young adolescents were having sex."
For the study, the researchers looked at the results of surveys of people born from 1984 to 1993. They found the following:
- About one in 200 females said they'd had sex by the age of 10, and it was non-consensual 62 percent of the time. Almost 1 percent had sex by the age of 12, and it was consensual almost 80 percent of the time.
- Surveys over the past 50 years suggest that no more than 10 percent of females have had sex by the age of 14.
- Pregnancy is rare until age 14, although many do get pregnant each year, including about 2,700 girls in 2008 aged 13 and under.
The study also looked at the use of contraception and found that older children were more likely to use it, including the 15- and 16-year-olds who can't get the Plan B contraceptive over the counter.
"The people who are most affected by that policy are the ones most likely to be having sex: 15- to 16-year-olds are far more likely than the youngest adolescents, the 10- to 11-year-olds," Finer said.
Amy Schalet, an assistant professor of sociology at the University of Massachusetts Amherst who studies teen sexuality, praised the study and said it shows that the "issues at stake" for younger kids are different than for older ones. "It is not common for those in their early teenage years to choose to have sex," she pointed out.
As for access to contraception, rates of teen pregnancy are high in the United States "in part because U.S. teens are less likely to consistently use the most reliable forms of contraception," she noted.
"One reason for that is that young people find it difficult to access contraception options, like the pill, which require them to talk to adults," Schalet said.
David Finkelhor, director of the University of New Hampshire's Crimes Against Children Research Center, has a more critical view of the study. He said it doesn't use the best strategies to study the sexual activities of teens because it relies too much on long-term remembrances of childhood sexuality.
Also, he said, "understanding the mix of coercive and consensual sex among teens is very important. To do this, you need a lot more details about the circumstances, such as alcohol usage."
The study is published in the May issue of the journal Pediatrics.
Explore further: CDC: Many teen moms didn't think it could happen
For more about teen sexual health, visit the U.S. National Library of Medicine.