PROJECT ABSTRACT The prevalence of opioid use disorder (OUD) during pregnancy is rising, increasing the incidence of severe maternal, neonatal, and obstetrical morbidity and mortality. Although maternal OUD can be effectively treated with buprenorphine, leading to improved adherence to prenatal care and reduced obstetrical complications, fewer than 1 in 5 patients receive medication treatment for maternal OUD. In large part, so few pregnant women receive buprenorphine because it can be challenging to initiate effectively. Initiation (termed buprenorphine induction) must begin while a patient is in moderate withdrawal. If induction begins too early, buprenorphine will displace the other opioid from the μ receptor, precipitating severe withdrawal. Maternal withdrawal, both precipitated and anticipated, is associated with high relapse rates, non-adherence and lower treatment retention rates. Unsurprisingly, induction is a known critical time point for dropout in OUD treatment. Multiple alternative protocols for buprenorphine induction have been reported, including successful methods that do not require an opioid-free period or moderate withdrawal symptoms by using microdoses of buprenorphine, such as via a transdermal patch, as a bridge induction method to full sublingual doses. However, buprenorphine induction protocols have never been studied in pregnancy to determine the most effective type. We propose a prospective, mixed-methods study at two OUD-specific prenatal clinics to evaluate the feasibility of conducting an randomized controlled trial (RCT) comparing buprenorphine transdermal bridge induction versus standard sublingual induction in pregnant patients with OUD. In Aim 1, we will qualitatively assess feasibility domains using semi- structured interviews with 20 patients using buprenorphine to treat maternal OUD, 10 clinical team members who treats them, and 5 research team members. We will present the RCT protocol to interviewees, and ask for feedback on consensus-based criteria of recruitment capability, assessment procedures, and acceptability. We will solutions, ask interviewees to conduct a “premortem” exercise to predict potential etiologies of RCT failure, brainstorm and adapt the RCT protocol accordingly. In Aim 2, we will quantitatively assess intervention and research methods feasibility (eg, percentage of recruitment/retention goals, success of masking, intervention fidelity) and preliminary efficacy to minimize withdrawal symptoms by conducting a pilot RCT of bridge versus standard buprenorphine induction to treat maternal OUD (n=20 per arm). Results will provide preliminary data to aid in design of large, multi-site trial powered to rigorously assess the efficacy of induction methods on important obstetric and neonatal outcomes. If this larger trial shows that the bridge buprenorphine induction protocol is effective in multiple populations, this treatment protocol could be widely disseminated to improve outcomes for patients w...