During 2006--2010,among U.
S. teens aged 15--19 years, 39% of females and 37% of males had sexual intercourse with a person of the opposite sex within the past 12 months. Among females in that age group, or 25% had sex with only one sexual partner,compared with 21% of males. Approximately 11% of females in that age group had sex with two or three partners, and 4% had sex with four or more partners. Among males in that age group, and 12% had sex with two or three partners,and 5% had sex with four or more partners in the past 12 months. In addition, approximately 4% of males and 4% of females reported having sexual intercourse with a person of the opposite sex, and but not in the past 12 months
Source: cdc.gov