One in four female teens, — an estimated 3.2 million girls in the United States — is infected with at least one of the most common sexually transmitted diseases, according to a study from the U. S. Centers for Disease Control and Prevention. The study, released this week at the 2008 National STD Prevention Conference, looked at the prevalence of STDs among adolescent women in the United States. It found that the human papillomavirus or HPV stood as the most common STD with 18 percent of teens girls infected. The study, based on an analysis of the 2003-2004 National Health and Nutrition Examination Survey, also found that African-American teenage girls were most severely affected. Nearly half of the young African-American women (48 percent) were infected with an STD. Two separate studies also released at the conference by CDC researchers found that contraceptive services are a missed opportunity for STD screening and prevention. One of those studies found that while 82 percent of sexually active 15- to-24 year-old young women receive contraceptive or STD/HIV services, only 39 percent received both.