African-American female adolescents who engage in oral, vaginal and anal sex: "Doing it all" as a significant marker for risk of sexually transmitted infection

African-American female adolescents who engaged in vaginal sex only (N = 272) were compared to adolescents who engaged in two types (vaginal plus oral or anal; N = 295) and three types (vaginal, oral and anal; N = 144) on a constellation of other sexual risk behaviors (SRBs) and on sexually transmitted infections (STIs). Adjusted contrasts among groups revealed that adolescents who engaged in two and in three types of sex as compared to those who engaged in vaginal sex only were more likely to engage in six of the seven SRBs, but were just as likely to have a STI. One SRB, having ≥ 4 lifetime sex partners, was in turn associated with STI. Two-way interactions indicated that having a casual sex partner and having multiple sex partners in the last 60 days increased the likelihood of STI, but only for adolescents who engaged in all three types.