Adolescence marks the period between childhood and adulthood when hormonal changes transform boys and girls into young men and women able to have children of their own. The percent of adolescents who are having sex at earlier ages has decreased since 1988 and contraceptive use has increased since the 1990s. Together these two factors have contributed to the U.S. reaching its lowest teen pregnancy and birth rates in years.,, Still, almost half of all high school students reported that they had had sexual intercourse in 2013 and one in eight adolescent females will become pregnant before turning 20. Condom and contraceptive use is critical for adolescents to prevent pregnancy and sexually transmitted diseases. Among sexually active adolescents, male high school students were more likely to use a condom the last time they had sex than were females (66 percent vs. 53 percent).
Dating during adolescence is common and can be part of healthy development. However, serious and exclusive dating relationships can lead adolescents to have sex earlier than they would have otherwise. Those who have sex at an early age are more likely to engage in risky sexual behaviors. Overall, the proportion of adolescents who have ever had sex has declined substantially since the early 1990s. Of adolescents who have had sex, approximately one-third has had just one partner. Sixteen percent has had two partners, 32 percent has had three to five partners, and 20 percent has had six or more partners. Many adolescents are engaging in sexual behaviors other than vaginal intercourse: nearly one-half have had oral sex, and just over one in 10 have had anal sex.
Latest estimates reveal that more than 614,000 teen girls in the United States learn they are pregnant each year. Although this number is the lowest in U.S. history, it is still higher than many other developed countries, including Canada and the U.K. Teen parents face multiple risks for poor life outcomes: often, they fail to finish high school and are more likely to be poor as adults. In all, one in eight adolescent females will give birth by her 20th birthday and this number is higher for black and Hispanic adolescents.  Children born to adolescents face particular challenges—they are more likely to have poorer educational, behavioral, and health outcomes throughout their lives, as compared to children born to older parents. Teen pregnancy is an issue that many people are working to address. One of HHS' key priorities is to reduce teen and unintended pregnancy.
Adolescents account for about half of all STDs diagnosed every year, even though they make up a much smaller percentage of the sexually active population. Today, four in 10 sexually active teen girls have had an STD that can cause infertility and even death. Also, though rates of HIV are very low among adolescents, males make up more than two-thirds of HIV diagnoses among 13- to 19-year-olds. STDs often have no obvious sign or physical symptom, so regular screenings are critical. The most effective way to prevent STDs is to abstain from sexual activity; if teens are having sex, they should be using a condom correctly and with every sexual act. 
Rates of teen pregnancy are higher in the U.S. than in other countries. Hormonal methods of birth control (such as the pill) and barrier methods (such as condoms) can reduce the risk of pregnancy, and condom use with every sexual act can greatly reduce—though not eliminate—the risk of STDs. Condom and contraceptive use among adolescents has increased since the 1990s, but many adolescents are inconsistent users: of those who had sex in the past month, almost one in four males and almost four in 10 females did not use a condom. 
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