HOUSTON, April 9 (UPI) -- By age 12, 12 percent of U.S. students had already engaged in vaginal sex, 7.9 percent in oral sex and 6.5 percent in anal sex, U.S. researchers have learned.

Christine Markham of the University of Texas School of Public Health and colleagues examined sexual risk behaviors among middle-school students in a large southeastern U.S. urban public school district.


"This is one of the few school-based studies conducted with this age group to look at specific sexual practices in order to develop more effective prevention programs," Markham said in a statement. "This study shows that although most seventh graders are not engaging in sexual risk behaviors, a small percentage are putting themselves at risk."

For the purposes of the study, Markham and colleagues defined sexual intercourse as vaginal, oral or anal sex.

The findings are alarming because youth who start having sex before age 14 are much more likely to have multiple lifetime sexual partners, use alcohol or drugs before sex and have unprotected sex, all of which puts them at greater risk for getting a sexually transmitted disease or becoming pregnant, Markham said.

The study, published in the Journal of School Health, said one-third of the sexually active students reported engaging in vaginal or anal sex without a condom within the past 3 months and one-fourth had four or more partners, the study said.