Teens at high risk of pregnancy who know about and have access to effective, long-acting birth control experience fewer unplanned pregnancies. These birth control methods include hormonal implants, hormonal and copper intrauterine devices, or IUDs, vaginal rings, hormone injections, and oral contraceptives. The results are based on a sampling of teens who took part in the St. Louis-based Contraceptive CHOICE Project, led by researchers at Washington University.

The mission of the CHOICE Project is to “remove financial barriers to contraception, promote the most effective methods of birth control, and reduce unintended pregnancy in the St. Louis Area.” Enrollment of almost 10,000 St. Louis women began in August of 2007 and covers a group diverse in age, education, and ethnicity.

A total of 1,404 teens took part in CHOICE between 2008 and 2013, and 97 percent reported that they had already lost their virginity by enrollment. By the end of the first year in the program, the percentage of the participating teens who were sexually experienced rose to 99 percent. Overall, the average annual rate of pregnancy for all of the teens combined was 34 per 1,000 teen women at risk. Compared with the national average of 57.4 per 1,000 in 2010, the CHOICE teens had 41 percent fewer pregnancies. Compared with the 158.5 annual pregnancies among American teens who were sexually active, the CHOICE teens had 79 percent fewer pregnancies.

After being informed of all available contraceptive methods, 35 percent of the teens chose hormone implant, 32 percent chose hormonal IUs, 13 percent chose pills, 9 percent chose injections, and 5 percent chose copper IUDs. Among those teens who chose hormonal implants or copper IUDs, not a single pregnancy occurred.

The results were similar for abortions and live births, according to the report, which was published this week in the New England Journal of Medicine. The average annual abortion rate for CHOICE participants was 9.7 per 1,000, compared with 14.7 per 1,000 in all American teens and 41.5 per 1,000 in all sexually active American teens. Live births per 1,000 for CHOICE teens numbered 19.4 compared with 34.4 for American teens and 94 for sexually active American teens.