Objective: To evaluate heavy menstrual bleeding treatment outcomes with levonorgestrel 52-mg intrauterine device (IUD) use in participants without body mass index (BMI) or parity restrictions. Methods: Investigators included participants aged 18-50 years with no pelvic or systemic pathology causing heavy menstrual bleeding at 29 U.S. centers in a prospective trial. Participants had up to three screening cycles with menstrual product collection for alkaline hematin blood-loss measurements. Investigators enrolled those with two menses with blood loss of 80 mL or more (values averaged for baseline blood loss), placed the IUD, and followed participants for up to six 28-day cycles. Participants collected any menstrual products used during cycles 3 and 6 for blood-loss measurement. We evaluated outcomes in participants with at least one follow-up assessment for the primary outcome of median absolute blood-loss change and, secondarily, treatment success, defined as the proportion with a final measured blood loss less than 80 mL and at least 50% reduction from baseline. We evaluated exploratory outcomes of differences in blood-loss changes by BMI and parity using Wilcoxon rank sum test. Results: Of 105 enrolled participants, 47 (44.8%) had obesity (BMI 30.0 or higher) and 29 (27.6%) were nulliparous. Baseline mean blood loss ranged from 73 to 520 mL (median 143 mL, interquartile range 112-196 mL). Eighty-nine (84.8%) had at least one evaluable follow-up evaluation. Participants had median (interquartile range) absolute blood-loss decreases at cycles 3 (n=86) and 6 (n=81) of 93.3% (86.1-97.7%) and 97.6% (90.4-100%), respectively. At cycle 6, participants without obesity (n=43) and with obesity (n=38) had similar median [interquartile range] decreases (97.6% [91.8-100%] and 97.5% [90.3-100%], respectively; P=.89), with comparable findings for nulliparous (n=25) and parous (n=56) participants (97.0% [91.7-99.1%] and 98.1% [89.9-100%], respectively; P=.43). Treatment success occurred in 81.8% (95% CI 74.2-89.4%) of 99 participants, excluding those with no outcomes due to lost to follow-up or consent withdrawal, and did not vary by BMI or parity. The most common adverse events leading to discontinuation were bleeding or cramping (n=6 [5.7%]) and expulsion (n=5 [4.8%]). Conclusion: This levonorgestrel 52-mg IUD reduces blood loss by more than 90% over 6 months compared with baseline for most users with heavy menstrual bleeding.