PROJECT SUMMARY: The surge in the non-medical use of prescription opioids, heroin, and fentanyl is a critical public health emergency affecting women of child bearing age and their families. Pregnancy can be a motivating time for women with opioid use disorder (OUD) to engage in treatment, with pharmacotherapy (with methadone or buprenorphine) and psychotherapy the recommended first line treatment. Pharmacotherapy adherence has been associated with improved obstetric, infant, and maternal substance use outcomes at delivery. Yet medication discontinuation in the postpartum period occurs at high rates, increasing the risk of relapse and overdose. To date, however, interventions to support pharmacotherapy adherence among pregnant women with OUD have shown mixed results, and few interventions have been aimed at postpartum women and families. Therefore, the central objective of this mixed-methods study is to quantify how OUD pharmacotherapy utilization impacts postpartum maternal-infant outcomes and qualitatively explore factors impacting treatment adherence in order to develop a pharmacotherapy promotion intervention to improve the health of the opioid- exposed mother-infant dyad. This project includes three main aims: (1) To analyze a linked, longitudinal, administrative dataset from Massachusetts Department of Public Health to examine how duration of pharmacotherapy engagement and type of pharmacotherapy received impact maternal and infant outcomes; (2) To engage with a diverse group of stakeholders including postpartum women with opioid use disorder and their families to qualitatively identify beliefs and attitudes and delineate interpersonal and structural barriers and facilitators to treatment engagement and adherence to develop a pharmacotherapy promotion intervention; and (3) Pilot test the pharmacotherapy intervention to improve treatment adherence among pregnant and postpartum women with OUD assessing the feasibility and acceptability of the intervention. The findings from this series of projects will fill an existing gap in a high priority research area within NIDA that will inform the care of pregnant and postpartum women with OUD. The PI, Dr. Schiff, is an early-career clinician investigator, pediatrician, and addiction medicine physician who will use this career development award to enhance her skills in quantitative research including longitudinal analyses of complex public health datasets, qualitative research with vulnerable populations, intervention development, and clinical trials design. Throughout the award period, Dr. Schiff will work closely with a multidisciplinary mentorship and advisory team with expertise in maternal-child health, addiction psychiatry, perinatal epidemiology, biostatistics, qualitative analysis, intervention development, and clinical trials design to carry out her stated career objectives and specific aims.