Objectives: We aimed to better understand emergency department (ED) use, admission patterns, and demographics for substance use disorder in pregnancy and postpartum (SUDPP)., Methods: In this longitudinal study, the United States Nationwide Emergency Department Sample was queried for all ED visits by 15- to 50-year-old women with a primary diagnosis defined by International Classification of Diseases, 9th or 10th edition Clinical Modification, codes of SUDPP between 2006 and 2016. Patterns of ED visit counts, rates, admissions, and ED charges were analyzed., Results: Annual national estimated ED visits for SUDPP increased from 2,919 to 9,497 between 2006 and 2016 (a 12.4% annual average percentage change), whereas admission rates decreased (from 41.9% to 32.0%). ED visits were more frequent among women who were 20-29 years old, using Medicaid insurance, in the lowest income quartile, living in the South, and in metropolitan areas. Compared with the proportion of ED visits, 15- to 19-year-olds had significantly lower admission rates, whereas women with Medicaid and in the lowest income quartile had higher admission rates (p < .001). Opioid use, tobacco use, and mental health disorders were most commonly associated with SUDPP. The ED average inflation-adjusted charges for SUDPP increased from $1,486 to $3,085 between 2006 and 2016 (7.1% annual average percentage change; p < .001), yielding total annual charges of $4.02 million and $28.53 million., Conclusions: Despite the decrease in admissions, the number and charges for ED visits for SUDPP increased substantially between 2006 and 2016. These increasing numbers suggest a continuous need to implement preventive public health measures and provide adequate outpatient care for this condition in this population specifically., (Copyright © 2022 Jacobs Institute of Women's Health, George Washington University. Published by Elsevier Inc. All rights reserved.)