The impact of prior levonorgestrel intrauterine device use at the time of embryo transfer.

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To investigate whether infertile women with a history of levonorgestrel intrauterine device (LNG IUD) use have impaired pre-transfer endometrial thickness and pregnancy rates after embryo transfer. Retrospective cohort study at a single academic medical center of infertile women ages 18-44 with a history of LNG IUD use undergoing their first embryo transfer cycle between January 2019 and January 2021 compared to controls with a history of no prior birth control use (NONE) or only prior oral contraceptive use (OCP). The primary outcome is endometrial thickness prior to embryo transfer. Secondary outcomes include embryo transfer results. We analyzed data from a total of 616 patients (197 NONE, 357 OCP, 62 LNG IUD). Women with a history of LNG IUD use had thinner endometrial stripes than women with a history of no prior birth control use (LNG IUD 8.93mm, NONE 10.32mm [aRR 0.88, 95% CI 0.80-0.97]), but not when compared to women with a history of OCP use (OCP 9.61mm [aRR 0.92, 95% CI 0.84-1.01]). Women with a history of LNG IUD use had slightly higher implantation rates than those with no birth control use history (LNG IUD 43.37%, NONE 24.17% [RR 1.79, 95% CI 1.21-2.45]), though not when compared to prior OCP users (OCP 38.72% [RR 1.12, 95% CI 0.86-1.47]). The remainder of the embryo transfer outcomes were similar between the three groups. Prior LNG IUD users have reduced endometrial thickness at the time of embryo transfer but do not have worse pregnancy outcomes.