Intrauterine adhesions and prior use of a progestin-releasing intrauterine device

Progestin-IUD use was more frequent among IUA cases (29.9%) than polyp (3.4%) or infertile (11.1%) comparison groups. Compared to infertile comparators, any prior progestin-IUD use was independently associated with IUA (aOR 3.12; 95% CI 2.01, 4.85). There was a duration-response pattern: use of 5 years or less was modestly associated with IUA case status (aOR 1.99; 1.09, 3.64), whereas use >5 years conferred more than a seven-fold increase (aOR 7.26; 3.27, 16.11). The association persisted among surgically naive women (aOR 3.98; 2.44, 6.48) and was concentrated in those who were nulliparous, where use beyond five years conferred an approximately twelve-fold increase in odds (aOR 12.74; 5.25, 30.92). Progestin-IUD use was less frequent in polyp controls relative to IUA and infertile comparators, suggesting a possible role for progestin exposure in preventing endometrial polyp formation. The case control design does not allow for estimation of absolute risk for an individual and cannot inform causation. Further prospective studies are needed to better assess the relationship between progestin-IUD's, particularly when used beyond five years, and adverse fertility outcomes.