Results of a California study appearing in The American Journal of Public Health showed that almost two thirds of babies born to teenage girls were fathered by men four to six years older than the girls themselves.

"Most people always assumed a couple of teens fooling around" caused a teen pregnancy, said researcher Mike Males of the University of California, Irvine. "But these are adult men, not [teenagers] in school, not part of the programs and countermeasures that groups have set up to fight teen pregnancy . . . It's a real complicating factor."

More than 500,000 babies are born to U.S. teens annually. (Source: The Associated Press.)