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Risk of Unintended Pregnancy

Intended vs actual contraceptive use

Women initially choosing injectable contraception had pregnancy rates similar to oral contraception and significantly worse than intrauterine or implantable contraception. This according to a study that provided reversible contraception to 9,252 women at 2 to 3 years of follow-up. Researchers found:

• During 20,017 woman-years, 615 unintended pregnancies were identified.

• Despite switching and discontinuation, women choosing an intrauterine or implantable contraception at baseline were much less likely to have an unintended pregnancy vs women selecting other methods.

• In intent-to-use (ITU) analysis, pregnancy rates were 5.3, 5.5, 2.0, 1.7 and 1.9 per 100 woman-years for women initiating oral, injectable, implantable, copper and hormonal intrauterine contraception at baseline, respectively.

• Adjusted hazard ratio for injectable compared to hormonal intrauterine contraception was 2.4.

• Delaying initiation of intrauterine or implantable contraception increased unintended pregnancies by 60% (aHR=1.6).

• In as-used analysis, pregnancy rates were 6.7, 1.6, 0.2, 0.6, and 0.2 per 100 woman-years for women using oral, injectable, implantable, copper, and hormonal intrauterine contraception, respectively.

Citation: Reeves MF, Zhao Q, Secura GM, Peipert JF. Risk of unintended pregnancy based on intended compared to actual contraceptive use. [Published online ahead of print January 21, 2016]. Am J Obstet Gynecol. doi: 10.1016/j.ajog.2016.01.162.