INTRODUCTION: Opioid use has increased significantly in recent years, including during pregnancy. Evidence suggests as many as one in four women receive opioid therapy to some extent during pregnancy. Concerns have emerged regarding potential increased fetal risks, including central nervous system effects. RESEARCH QUESTION OR HYPOTHESIS: The purpose of this work is to describe clinical and demographic characteristics of patients receiving opioid therapy during pregnancy. STUDY DESIGN: Retrospective observational study. METHODS: Pregnant members of a Midwestern integrated health care system who delivered a live birth between 2006 and 2014 and had continuous pharmacy benefits beginning three months prior to their estimated pregnancy start through three months after their known delivery date were included. As part of a larger study aimed at understanding opioid prescribing patterns during pregnancy, demographic, clinical, and healthcare utilization variables of interest were identified and described. Opioid use during pregnancy was defined as more than five days in any three month-period, excluding the two-week period following delivery. RESULTS: Of 11,565 deliveries during the study period, 862 (7.4%) representing 816 unique patients were associated with opioid use during pregnancy. Fifteen percent of Medicaid beneficiaries received opioids during pregnancy versus 5% of commercially insured patients. Adjusting for Medicaid coverage, patient characteristics associated with an increased likelihood of receiving opioid therapy include: single marital status (OR = 1.19), current smoking status (OR = 2.42), a history of substance abuse (OR = 3.87), and mental health diagnoses (anxiety OR = 2.66, bipolar OR = 2.38, depression OR = 2.42). In addition, the use of non-opioid analgesics and mood-altering agents (e.g., benzodiazepines, antidepressants) were associated with increased opioid use. CONCLUSION: Opioid use was more common among single women who smoke, or have a mental health diagnosis or history of substance abuse. Women with these risk factors may benefit most from targeted outreach to decrease opioid use during pregnancy.