Perfect-use and typical-use Pearl Index of a contraceptive mobile app

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d3698147e173">Objectives</h5> <p id="P1">The Natural Cycles application is a fertility awareness-based contraceptive method, which uses dates of menstruation and basal body temperature to inform couples whether protected intercourse is needed to prevent pregnancies. Our purpose with this study is to investigate the contraceptive efficacy of the mobile application by evaluating the perfect- and typical-use Pearl Index. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d3698147e178">Study Design</h5> <p id="P2">In this prospective observational study, 22,785 users of the application logged a total of 18,548 woman-years of data into the application. We used these data to calculate typical- and perfect-use Pearl Indexes, as well as 13-cycle pregnancy rates using life-table analysis. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d3698147e183">Results</h5> <p id="P3">We found a typical-use Pearl Index of 6.9 pregnancies per 100 woman-years (95% CI: 6.5–7.2), corrected to 6.8 (95% CI: 6.4–7.2) when truncating users after 12 months. We estimated a 13-cycle typical-use failure rate of 8.3% (95% CI: 7.8–8.9). We found that the perfect-use Pearl Index was 1.0 pregnancies per 100 woman-years (95% CI: 0.5–1.5). Finally we estimated that the rate of pregnancies from cycles where the application erroneously flagged a fertile day as infertile was 0.5 (95% CI: 0.4–0.7) per 100 woman-years. We estimated a discontinuation rate over 12 months of 54%. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d3698147e188">Conclusions</h5> <p id="P4">This study shows that the efficacy of a contraceptive mobile application is higher than ususally reported for traditional fertility awareness-based methods. The application may contribute to reducing the unmet need for contraception. </p> </div>