Kathryn Kost and Stanley Henshaw of the Guttmacher Institute in New York said after peaking in the early 1990s, the U.S. teen pregnancy rate dropped by 37 percent among Hispanics, 48 percent among blacks and 50 percent among non-Hispanic whites.
In 2008, the U.S. teen pregnancy rate was 67.8 pregnancies per 1,000 women ages 15-19, which means about 7 percent of U.S. teens became pregnant that year -- a 42-percent decline from the peak in 1990 at 116.9 per 1,000.
Similarly, the teen birthrate declined 35 percent between 1991 and 2008, from 61.8 to 40.2 births per 1,000 teens; the abortion rate declined 59 percent from its 1988 peak of 43.5 abortions per 1,000 teens to its 2008 level of 17.8 per 1,000.
"The recent declines in teen pregnancy rates are great news," Kost, the lead author, said in a statement.
A large body of research has shown the long-term decline in teen pregnancy, birth and abortion rates was driven primarily by improved use of contraception among teens -- driven by increased use of the most effective contraceptive methods such as the pill versus condoms, as well as dual method use, using two forms of birth control, the study said.
There was also a decrease during the 1990s in the overall proportion of females ages 15-19 who were sexually experienced, but there has been almost no change in the proportion in recent years, the researchers said.