Early sexual activity is associated with emotional100 and physical health risks. Youth who engage in sexual activity are at risk of contracting sexually transmitted infections (STIs) and becoming pregnant. STIs, including HIV, can infect a person for a lifetime and have consequences including disability and early death. Meanwhile, delaying sexual initiation is associated with a decrease in the number of lifetime sexual partners,101 and decreasing the number of lifetime partners is associated with a decrease in the rate of STIs.102, 103 Additionally, teen pregnancy is associated with a number of negative risk factors, not only for the mother but also for her child (see FAM6).
Indicator Beh4: Percentage of high school students who reported ever having had sexual intercourse by gender and selected grades, selected years 1991–2009

NOTE: Students were asked, "Have you ever had sexual intercourse?" Data are collected biennially.
SOURCE: Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Youth Risk Behavior Surveillance System.
BEH4.A HTML Table, BEH4.B/C HTML Table
100 Meier, A.M. (2007). Adolescent first sex and subsequent mental health. American Journal of Sociology 112 (6): 1811–1847.
101 Chandra, A., Martinez, G.M., Mosher, W.D., Abma, J.C., and Jones, J. (2005). Fertility, family planning, and reproductive health of U.S. women: Data from the 2002 National Survey of Family Growth. Vital and Health Statistics, 23 (25). Hyattsville, MD: National Center for Health Statistics.
102 Dunne, E.F., Unger, E.R., Sternberg, M., McQuillan, G., Swan, D.C., Patel, S.S., and Markowitz, L.E. (2007). Prevalence of HPV infection among females in the United States. Journal of the American Medical Association, 297 (8), 813–819.
103 Gottlieb, S.L., Pope, V., Sternberg, M.R., McQuillan, G.M., Beltrami, J.F., Berman, S.M., and Markowitz, L.E. (2008). Prevalence of syphilis seroreactivity in the United States: Data from the National Health and Nutrition Examination Surveys (NHANES) 2001–2004. Sexually Transmitted Diseases, 35 (5), 507–511.
104 Centers for Disease Control and Prevention. 2009 Youth Risk Behavior Survey data. Available at http://apps.nccd.cdc.gov/youthonline/App/Default.aspx.