Topic DAT18-06: The prevalence of opioid use disorder (OUD) during pregnancy has quadrupled over the past decade, as have maternal and neonatal morbidity and mortality related to substance use. Medication- assisted treatment (MAT) use during pregnancy reduces adverse outcomes and is the recommended, evidence-based practice (EBP) for OUD treatment during pregnancy. Despite this, 40% of pregnant women with OUD do not receive MAT. Currently, there are no effective strategies to expand MAT access and availability for pregnant women, especially in rural, low-resource settings where maternal opioid use is disproportionately high. As an initial step to address this gap, we engaged key stakeholders across a large health system in Pennsylvania to determine barriers and facilitators to expanding treatment services in high need, low-resource obstetric settings. Our stakeholders identified a critical need for a women-centered, low- resource, sustainable, provider-level intervention to facilitate the adoption of MAT in obstetric settings. Therefore, our objective in this application is to test the effectiveness of a prenatal provider education and training program designed to facilitate the adoption of EBP for OUD during pregnancy called Project STEPuP (Substance abuse Treatment and Education during Pregnancy and Postpartum). Project STEPuP, grounded in preliminary and pilot work conducted by our research team, has 4 components designed to address barriers to MAT and EBP adoption: 1) a ?hub and spoke,? remotely-supported provider education and training program, 2) addiction teleconsultation support, 3) case management and telepsychiatry support, and 4) a partnership with health system administrators and payers to address administrative and reimbursement related needs. To achieve this objective, we will conduct a cluster-randomized clinical trial across 12 obstetric sites in Pennsylvania and New York. Outcomes among 870 patients will be assessed during pregnancy, at delivery and through 1 year postpartum. Our central hypothesis is that Project STEPuP will facilitate EBP adoption, increase MAT utilization and improve health outcomes among pregnant and postpartum women with OUD and their children. Specifically, we aim to: 1) create organizational readiness to facilitate Project STEPuP implementation; 2) assess the effect of Project STEPuP on provider adoption of EBP for OUD during pregnancy; and 3) evaluate the effect of provider adoption of EBP on maternal and child health outcomes. Our research is significant by addressing the substantial knowledge gap of how to increase MAT use in pregnancy and innovative by examining the role that prenatal providers can play in expanding treatment access.