Objective: To investigate the risk of abnormal perinatal outcomes in young patients with diminished ovarian reserve (DOR). Design: A retrospective cohort study. Setting: Reproductive medicine center in a hospital. Patients: A total of 5,649 young patients (<= 35 years) undergoing assisted reproductive technology for fresh -cycle ET between January 1, 2016, and January 31, 2019, were included. The patients were divided into two groups: the non-DOR group (n = 5,295) and the DOR group (n = 354). Intervention(s): None. Main Outcome Measure(s): Singleton live births were assessed for obstetrical complications and adverse birth outcomes. Result(s): There were signi fi cantly lower rates of clinical pregnancy, live birth, and singleton live birth among young patients with DOR, without an increase in the rates of clinical pregnancy loss, biochemical pregnancy, and multiple live births compared with young patients without DOR. For young patients with singleton live births, there were no signi fi cant differences in the incidence of gestational hypertension, gestational diabetes mellitus, placenta previa, fetal malformation, macrosomia, low birth weight, or preterm birth be- tween the two groups after adjusting with a multiple logistic regression model. Conclusion(s): We found that young patients with DOR still had acceptable pregnancy outcomes and similar risks of biochemical preg- nancy, pregnancy loss, multiple live births, and abnormal perinatal outcomes compared with young patients with normal ovarian reserve. (Fertil Steril (R) 2020;114:118-24. (C) 2020 by American Society for Reproductive Medicine.)