Contraceptive efficacy and safety of the 52-mg levonorgestrel intrauterine system for up to 8 years: findings from the Mirena Extension Trial.
Level 3 - non-randomized controlled study
Prospective single-arm follow-up extension study without a comparator group
PubMed 36096186 · doi:10.1016/j.ajog.2022.09.007
What was done
The US multicenter Mirena Extension Trial evaluated the efficacy, safety, and bleeding profiles of extended use of the 52-mg levonorgestrel-releasing intrauterine system (LNG-IUS) from year 6 through year 8. Investigators enrolled 362 individuals aged 18 to 35 years who had already used the device for 4.5 to 5 years. Contraceptive efficacy was assessed using the Pearl Index and Kaplan-Meier cumulative failure rates. Bleeding patterns, adverse events, user satisfaction, and 12-month return to fertility among those desiring pregnancy were also tracked.
What was found
Of 362 participants starting year 6, 223 completed 8 full years. Two on-treatment pregnancies occurred (one of undetermined location in year 6 and one ectopic in year 7; both resolved without surgery). For years 6 through 8, the overall Pearl Index was 0.28 (95% CI, 0.03-1.00), and the 3-year cumulative failure rate was 0.68% (95% CI, 0.17-2.71). Annual Pearl Indexes were 0.34 (year 6), 0.40 (year 7), and 0.00 (year 8). The 3-year ectopic pregnancy Pearl Index was 0.14 (95% CI, 0.00-0.77). Treatment-emergent adverse events occurred in 68.8% (249/362) of participants, with 18.0% (65/362) considered device-related. Overall discontinuation was 38.4% (139/362), most commonly due to desire for pregnancy (12.2%, 44/362). Among completers, 98.7% (220/223) reported satisfaction, and approximately half experienced amenorrhea or infrequent bleeding. Among 31 women with evaluable data who discontinued to conceive, 77.4% (24/31) achieved pregnancy within 12 months.
Why it matters
These data confirm that the 52-mg LNG-IUS provides robust, safe contraception for up to 8 years, extending its clinical utility beyond original 5-year approvals and reducing the frequency of device replacement procedures.
Limits
The study was a single-arm trial without a randomized comparator group. There was substantial attrition over the 3-year extension period (139/362 discontinued, 38.4%). The sample size was insufficient to evaluate extended efficacy specifically for the treatment of heavy menstrual bleeding, and participants older than 35 years at enrollment were excluded.
Cited by
- supports The Mirena levonorgestrel intrauterine device lasts for up to eight years for contraception and five years for heavy menstrual bleeding.