BACKGROUND: Although it is uncommon, the incidence of endometrial cancer and atypical hyperplasia among reproductive-aged women is increasing. The fertility outcomes in this population are not well described. OBJECTIVE: We aim to describe the patterns of care and fertility outcomes of reproductive-aged women with endometrial cancer or atypical hyperplasia. MATERIALS AND METHODS: A cohort of women aged 45 years with endometrial cancer or atypical hyperplasia diagnosed in 2000 to 2014 were identified in Truven Marketscan, an insurance claims database of commercially insured patients in the United States. Treatment information, including use of progestin therapy, hysterectomy, and assisted fertility services, was identified and collected using a combination of Common Procedural Terminology codes, International Statistical Classification of Diseases and Related Health Problems codes, and National Drug Codes. Pregnancy events were identified from claims data using a similar technique. Patients were categorized as receiving progestin therapy alone, progestin therapy followed by hysterectomy, or standard surgical management with hysterectomy alone. Multivariable logistic regression was performed to assess factors associated with receiving fertility-sparing treatment. RESULTS: A total of 4007 reproductive-aged patients diagnosed with endometrial cancer or atypical hyperplasia were identified. The majority of these patients (n ¼ 3189; 79.6%) received standard surgical management. Of the 818 patients treated initially with progestins, 397 (48.5%) subsequently underwent hysterectomy, whereas 421 (51.5%) did not. Patients treated with progestin therapy had a lower median age than those who received standard surgical management (median age, 36 vs 41 years; P < .001). The proportion of patients receiving progestin therapy increased significantly over the observation period, with 24.9% treated at Harrison et al. Fertility conservation and pregnancy outcomes in young women with endometrial cancer or hyperplasia. Am J Obstet Gynecol 2019.