PROJECT SUMMARY/ABSTRACT The prevalence of opioid use disorder (OUD) among women giving birth in US hospitals increased by 131% from 2010-2017. This corresponds directly to the 82% increase in neonatal opioid withdrawal syndrome (NOWS) diagnoses in the same period, up to 7/1000 hospital births.1,2 Despite the need for maternal OUD treatment, referrals from postpartum units and neonatal intensive care units (NICU) to OUD treatment are low and postpartum treatment dropout is high among those who were treated prenatally.3 Infants born to women with OUD are often sent to NICUs after birth to manage opioid withdrawal, with their mothers at their bedside during their stay. An infant's NICU stay therefore represents a critical period in which to diagnose maternal OUD, initiate treatment, and refer for ongoing care in a setting that prioritizes and preserves maternal-infant dyadic bonding. Despite recommendations to integrate maternal mental health screenings and referrals in pediatric settings and a global move towards integrated mental health and substance abuse treatment in adult healthcare settings, limited information exists on how to close the gap in maternal mental health and substance abuse treatment in pediatric settings. The major challenge we aim to address is the need for adult treatment to occur in a pediatric treatment setting where structures do not yet exist to make this feasible. The goals of this study are 1) to systematically identify the primary facilitators and barriers to implementing bedside OUD treatment in the NICU through in-depth interviews with mothers, NICU providers, and other stakeholders; 2) to use steps from implementation mapping to develop a suite of implementation strategies to collocate buprenorphine induction for postpartum women with OUD in the NICU based on feedback from Aim 1; and 3) to refine, test, and examine the acceptability and feasibility of applying the adapted model in a pilot case series in two NICU sites for use in larger trials. This process will allow us to deliver a treatment model and set of implementation strategies for providing evidence-based OUD treatment to postpartum mothers in NICUs that will enhance its accessibility and sustainability. Future goals include testing the intervention and implementation strategies in a subsequent hybrid effectiveness- implementation study to estimate the extent to which they lead to improved implementation, sustained treatment, and outcomes for new mothers with OUD.