Narrator: There may be a better way to avoid unwanted teen pregnancy. This is Science Today. Dr. Philip Darney of the University of California, San Francisco compared three methods of birth control among 400 teenagers: condoms, the pill, and Norplant, a contraceptive delivery system that's surgically implanted in the arm.

Darney: Teens who elected to use Norplant were much less likely to become pregnant, in fact none of them became pregnant in the first year.

Narrator: And they had no more sexually transmitted diseases than the teens who used only condoms. Darney thinks that's because the Norplant users were more motivated to avoid pregnancy and disease.

Darney: For example, they were more likely to have been pregnant in the past, they were more likely to have the support of their partners. They were more likely to come from a family with more contact with the father. So we think they were at inherently less risk of contracting a sexually transmitted disease than were the teens who chose not to use Norplant.

Narrator: Darney says it's a lesson for family planning clinics around the country. For Science Today, I'm Steve Tokar.