Reported expulsion and displacement of the levonorgestrel-releasing intrauterine system in women with adenomyosis: a systematic review and meta-analysis

The levonorgestrel-releasing intrauterine system (LNG-IUS) is widely used for adenomyosis, but expulsion and displacement may compromise treatment. We estimated their study-reported cumulative proportions and compared fixed or modified placement with conventional placement. PubMed, Embase, Web of Science Core Collection, CENTRAL, and Scopus were searched from inception to July 2026. Random-effects models pooled proportions and risk ratios (RRs) with 95% confidence intervals (CIs). Follow-up subgroups, common-time-point sensitivity analyses, and a binomial generalized linear mixed model (GLMM) were examined. Certainty of evidence was assessed using GRADE. 30 studies reporting 3,536 participants overall were included. Across 24 studies (2,443 participants), the pooled cumulative proportion of reported expulsion was 7.3% (95% CI, 3.7%–11.7%), with substantial heterogeneity (I² = 89.55%) and a 95% prediction interval of 0.0%–34.7%. Proportions were 2.8% (95% CI, 0.8%–5.6%) and 13.6% (95% CI, 6.9%–22.0%) in studies with nominal follow-up of ≤ 12 and > 12 months, respectively ( P = 0.004 for the subgroup difference). Separate analyses at exact 6- and 12-month endpoints yielded approximately 3% and 4%, respectively, in different sets of studies. The GLMM estimate for reported expulsion was 5.8% (95% CI, 3.1%–10.4%). Across seven studies (329 participants), the pooled reported-displacement proportion was 0.8% (95% CI, 0.0%–2.5%). Exploratory comparisons associated fixed or modified placement with less reported expulsion (two nonrandomized studies; RR, 0.12; 95% CI, 0.03–0.49) and fewer displacement-or-expulsion composite events (one randomized and one nonrandomized study; RR, 0.28; 95% CI, 0.15–0.54). Certainty was very low for the graded outcomes; no single GRADE rating was assigned to the mixed-design pooled composite estimate. Study-reported LNG-IUS expulsion and displacement occur in women with adenomyosis, but heterogeneity in follow-up, outcome definitions, and ascertainment, together with very low-certainty evidence, limits interpretation. The low reported frequency of displacement may underestimate positional abnormalities because asymptomatic cases can be missed without systematic imaging. Exploratory comparisons do not establish a clinical benefit of fixed or modified placement or support its routine use.