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

Abstract: Our objective is to investigate whether infertile women with a history of levonorgestrel intrauterine device (LNG IUD) use have impaired endometrial growth and pregnancy rates after embryo transfer. This is a retrospective cohort study at a single academic medical center of infertile women aged 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 prior oral contraceptive (OCP) use. The primary outcome is endometrial thickness prior to embryo transfer. Secondary outcomes are embryo transfer results, including implantation, miscarriage and live birth. Demographic, baseline and cycle characteristics were similar among the three groups. Women with a history of LNG IUD use had thinner endometrial stripes than women with a history of NONE (LNG IUD: 8.93 mm, NONE: 10.32 mm (aRR: 0.88, 95% CI: 0.80-0.97)) but not when compared to women with a history of OCP use (OCP: 9.61 mm (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 NONE history (LNG IUD: 43.37%, NONE: 24.17% (relative risk (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 among the three groups. In conclusion, prior LNG IUD users have a reduced endometrial thickness at the time of embryo transfer but do not have worse pregnancy outcomes. Lay summary: LNG IUDs (brand names include Mirena, Liletta and Skyla) are some of the most widely used forms of birth control. While these devices are safe and are generally not believed to impact fertility, a few recent articles have suggested the possibility of a long-term impact of prior intrauterine device use on the uterine lining in some patients. As such, we sought to examine uterine lining growth and outcomes of assisted reproduction in an infertile patient population with a history of LNG IUD use compared to infertile women without a history of LNG IUD use. Ultimately, we found that women with a history of LNG IUD use had less uterine lining growth during assisted reproduction cycles, but that they did not have worse pregnancy outcomes when compared to women without a history of levonorgestrel device use.