Objective: The objective was to describe the endometrial milieu of stable transplant patients and healthy women before and after levonorgestrel intrauterine system (LNG-IUS) insertion. Study design: Women between 18 and 45 years of age desiring LNG-IUS insertion were enrolled with a 2:1 ratio of healthy to stable solid organ transplant patients. The first visit entailed a blood draw, uterine lavage and endometrial biopsy followed by LNG-IUS insertion. Follow-up visit involved a repeat serum draw, uterine lavage and endometrial biopsy. Cytokine levels were measured in the uterine lavage and serum by quantifying inflammatory biomarkers. Immunohistochemistry staining was performed on the endometrial tissue to measure macrophage levels. Statistical analysis included a nonparametric analysis that compared medians of the marker levels before and after intrauterine device (IUD) insertion within the group and between the two groups. Results: Sixteen participants completed the study: 5 solid organ transplant patients and 11 healthy patients. For the serum, there were no marked changes in the cytokines or soluble receptor levels in either group after IUD insertion. However, in the uterine lavage, there was an increase in cytokine levels post-IUD insertion for both healthy and transplant women. For the endometrial tissue, there was evidence of macrophage activity in both groups after device insertion. Conclusions: This pilot study investigated the uterine environment of the transplant patient population. Findings have pointed to the strong local inflammatory response following LNG-IUS insertion for the transplant recipients. In addition, these preliminary findings will help power a larger study that can investigate the safety and effectiveness of the IUD in this patient population. (C) 2016 The Authors. Published by Elsevier Inc.