Two-thirds of sexually active teenage girls are having sex with boys close to their own age, according to a study that also found that those girls who have older partners are much more likely to end up with babies.
By looking at all teen sex, not just liaisons that lead to childbirth, the new data refine earlier research that found most teen mothers had older partners.
Only about 7 percent of sexually active girls ages 15 to 17 had partners who were at least six years older than they were. But these girls accounted for 19 percent of the teen pregnancies, according to the study published in Family Planning Perspectives, the research journal published by the Alan Guttmacher Institute.
These couples were less likely to use contraception, and girls who got pregnant were less likely to have abortions than their peers involved with younger men. As a result, they make up a disproportionate share of the teen mothers, facing an increased risk of poverty, welfare and dropping out of school.
"You're dealing with a relatively small number of young women," said Jeannie Rosoff, president of Guttmacher. Still, she added: "If I had my 15-year-old going out with an older guy, I would probably be pretty panicked."
Nearly four in 10 girls ages 15 to 17 have had sex at least once, government surveys find, but this is the first look at the age of their partners. Women of all ages tend to have older sexual partners _ more so for older women than for teenagers, as age differences become less significant with age.
This study, which used data from a 1995 government survey of families, found that 64 percent of sexually active girls ages 15 to 17 had partners who were within two years of their age. Another 29 percent had sex with partners three to five years older.
Two-thirds of girls with men six and more years older than they are used contraception, compared with three-quarters of girls with boys close to their own age. Girls with younger boys who got pregnant were nearly twice as likely to abort than girls with older men.
The question is why girls who are with older men seem more willing to get pregnant _ and to carry those pregnancies to term.
Many suggest that men are taking advantage of their younger, more vulnerable partners.
Patterns of contraception may offer a less nefarious explanation. Earlier studies have found that as men get older, they are less likely to use condoms. That is usually offset by their female partners, who start using birth-control pills and other methods of contraception as they get older.
Researchers hope the study will clarify earlier work that found most teenage mothers had older partners _ data seized by some lawmakers who blamed predatory older men for the problems of teen pregnancy.