Research news: July 2012

N Engl J Med2012 366:998-2007

Between 2007 and 2011 US researchers recruited 7486 girls and women from St Louis for a comparative study of contraceptive methods. Most (5781) chose an intrauterine device (IUD) or subdermal implant after reading a leaflet explaining these were the most effective methods, but 1527 chose a contraceptive pill, patch, or vaginal ring and 176 chose a depot injection of medroxyprogesterone acetate. All contraceptives were free of charge.

Over the next three years, there were 156 pregnancies caused by contraceptive failure. In fully adjusted analyses, reversible long acting contraceptives (IUDs and implants) were 20 times more effective than pills, patches, or rings (21/5781 pregnancies v 133/1527, hazard ratio for pills patches or rings 21.8 (95% CI 13.7 to 34.9)). Depot injections were also highly effective, and both long acting contraceptive methods worked equally well for teenagers and older women in the cohort. The study was paid