Perinatal Substance Use Disorders (SUDs) affect up to 10% of pregnant and newly postpartum people. An enormous amount of stigma and shame prevents many of these patients from seeking much-needed care. This first of a two-part series explores the reasons for, and presentations of, Perinatal SUDs, as well as strategies for engaging patients in care, including Los Angeles County’s Plans of Safe Care initiative. We also begin reviewing interventions for specific SUDs by discussing tobacco use disorder and appropriate perinatal treatments.