Contraceptive Efficacy and Comparative Side Effects of a Mini Copper Intrauterine Device.

Background: Intrauterine devices (IUDs) are highly effective, yet acceptability and continuation differ by user and device characteristics. We evaluated the efficacy of the NTCu380 Mini, a 380-mm copper IUD available in Europe and Canada, and compared safety and continuation with the TCu380A IUD, the 380-mm copper IUD available in the United States.

Methods: We randomly assigned participants between 16 and 40 years of age in a 4:1 ratio to the NTCu380 Mini or TCu380A and assessed over 37 months. The primary outcome was NTCu380 Mini efficacy measured by the Pearl Index (defined as the number of pregnancies per 100 woman-years) in participants 35 years of age and under. Additional outcomes included NTCu380 Mini time to pregnancy by survival analysis, and comparative adverse events (AEs) and continuation rates of NTCu380 Mini versus TCu380A.

Results: We randomly assigned 887 participants to NTCu380 Mini (744 [83.9%] nulliparous) and 218 to TCu380A (183 [83.9%] nulliparous), of whom 875 (98.6%) and 213 (97.7%), respectively, had successful placement. The NTCu380 Mini IUD 3-year cumulative Pearl Index was 1.86 (95% confidence interval [CI], 1.20 to 2.74) pregnancies per 100 women-years; the cumulative rate of pregnancy through year 3 was 4.8% (95% CI, 2.8 to 6.9%). Serious AEs occurred in 31 (3.5%) NTCu380 Mini and 4 (1.9%) TCu380A users (P=0.28). Discontinuation occurred in 449 (51.3%) NTCu380 Mini and 122 (57.3%) TCu380A users (P=0.07). AEs led to discontinuation less frequently among NTCu380 Mini (152 [20.8%]) than TCu380A users (57 [33.2%]) (P=0.001), particularly bleeding or pelvic pain AEs (103 [14.5%] vs. 46 [27.3%], respectively; P<0.001).

Conclusions: In this predominantly nulliparous population, the NTCu380 Mini IUD had an approximate 5% pregnancy rate over 3 years, with fewer side effects leading to discontinuation than observed among TCu380A users. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov number, NCT03124160.) The findings and conclusions in this article are those of the authors and do not necessarily reflect the views of the Planned Parenthood Federation of America, Inc.