Researchers provided free, FDA-approved birth control to the women for three years. The women were given their choice of contraception, including oral birth control pills and long-acting reversible contraceptive (LARC) methods like implants and IUDs. The researchers specially briefed the participants on the “superior effectiveness” of LARC methods — the T-shaped IUD, or intrauterine device, has close to 100% effectiveness and can last five to 10 years, for instance — and 75% of women chose those devices over the pill, patch or ring.
Over the course of the study, which lasted from 2008 to 2010, women experienced far fewer unintended pregnancies than expected: there were 4.4 to 7.5 abortions per 1,000 women in the study, after adjusting for age and race — much fewer than the national rate of 19.6 abortions per 1,000 women and lower also than the rate in the St. Louis area of 13.4 to 17 abortions per 1,000 women.
The effect of free contraception on the teen birth rate was remarkable: there were 6.3 births per 1,000 girls aged 15 to 19 in the study, compared with the national rate of 34.3 births per 1,000 teen girls.
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Study: Free Birth Control Slashes Abortion Rates | TIME.com