Background: The unprecedented increase in population around the globe has led to considering family planning policies in recent decades. Intrauterine device (IUD) is one of the most effective methods of contraception; yet, this method is associated with complications and problems that cause its removal.Objectives: This study aims to evaluate mastalgia and the complications attributed to it following Mirena IUD in women referring to medical centers in Yazd.Methods: In this prospective cohort study, 201 women using Mirena IUD who referred to the Gynecology Ward of two public and private hospitals in Yazd province were followed up for 6 months from November 2021 to June 2022. Data were gleaned using a data questionnaire including age, parity, duration of IUD use, and IUD complications and analyzed with SPSS22 using descriptive and analytical statistical chi-square.Results: Of 201 women studied, 48 (36.9%) reported mild mastalgia, 7 (3.5%) had moderate mastalgia, and 12 (6%) reported severe mastalgia after IUD insertion. After 6 months, 54 (37.9%) participants had mild mastalgia, 10 (5%) reported moderate mastalgia, and 12 (6%) reported severe mastalgia. Moreover, among the complications of IUD, menstrual spotting was reported in the majority of participants (57.2%), followed by pelvic pain (28.9%), dyspareunia (27.9%), and nausea (17.4%) as the most common complications, respectively.Conclusion: According to this study, mastalgia in women using IUD is the most common complication, second to abnormal uterine bleeding, and is not related to the age and parity of the participants. Also, IUD breast complications are relatively common, and more studies are needed to investigate these complications
