SEX, PREGNANCY AND ABORTION
• Although only 13% of U.S. teens have had sex by age 15, most initiate sex in their late teen years. By their 19th birthday, seven in 10 teen men and teen women have had intercourse.
• Between 1988 and 2006–2010, the proportion of never-married teens aged 15–17 who had ever engaged in sexual intercourse declined from 37% to 27% among females, and from 50% to 28% among males. During the same period, among teens aged 18–19, that proportion declined from 73% to 63% among females, and 77% to 64% among males.
• The pregnancy rate among young women has declined steadily, from 117 pregnancies per 1,000 women aged 15–19 in 1990 to 68 per 1,000 in 2008. 
• The majority (86%) of the decline in the teen pregnancy rate between 1995 and 2002 was the result of dramatic improvements in contraceptive use, including an increase in the proportion of teens using a single method of contraception, an increase in the proportion using multiple methods simultaneously and a substantial decline in nonuse. Just 14% of the decline is attributable to decreased sexual activity.
• Of the approximately 750,000 teen pregnancies that occur each year, 82% are unintended. Fifty-nine percent end in birth and more than one-quarter end in abortion.
• In 2009, there were 39.1 births per 1000 women aged 15–19, marking a historic low in the birthrate. This rate represents a 37% decline from the peak rate of 61.8 in 1991.
• The 2008 teenage abortion rate was 17.8 abortions per 1,000 women. This figure was 59% lower than its peak in 1988, but 1% higher than the 2005 rate.
• Compared with their Canadian, English, French and Swedish peers, U.S. teens have a similar level of sexual activity, but they are more likely to have shorter and less consistent sexual relationships, and are less likely to use contraceptives, especially the pill or dual methods.
• The United States continues to have one of the highest teen pregnancy rates in the developed world (68 per 1,000 women aged 15–19 in 2008)—more than twice that of Canada (27.9 per 1,000) or Sweden (31.4 per 1,000).
• Every year, roughly nine million new STIs occur among teens and young adults in the United States. Compared with rates among teens in Canada and Western Europe, rates of gonorrhea and chlamydia among U.S. teens are extremely high.[9, 10]
From here, where there is more information, and the data is sourced.