Background: Despite the high efficacy of intrauterine contraception (IUC), pregnancies can occur with IUC in situ. Studies examining pregnancy outcomes with IUC in situ were done on patients with copper intrauterine device (Cu-IUD) with limited studies that examine pregnancy outcomes with levonorgestrel-releasing intrauterine system (LNG-IUS). Outcomes with LNG-IUS may be different from that of Cu-IUD and more studies are needed to evaluate these outcomes in order to inform practice. Objectives: The primary objective of our study is to compare the proportion of spontaneous abortions (SAB) among women who conceive with LNG-IUS in place compared to women who conceive with no LNG-IUS in place. Methods: This will be a retrospective cohort study of women seen in the University of North Carolina Health Care System from 2003 to 2012. Identification of the LNG-IUS group will be by ICD-9 code 966.32 (pregnancy with an IUC in place) and medical record documentation that confirms the IUC is LNG-IUS. The comparison group will be all other women who were diagnosed with a pregnancy during the same time period. The primary outcome is the rate of SAB prior to 20 weeks in LNG-IUS users. We hypothesize that there will be an increased risk of SAB in the LNG-IUS group compared to the no IUC group. Significance: The knowledge gained from this research may change our management and counseling for patients that conceive with LNG-IUS in situ.