Background <p>Substance use has increased among pregnant and postpartum people in the last decade, yet few pregnant individuals receive prenatal care and treatment for substance use disorder (SUD). The Nurture Oregon model aims to integrate medical care with SUD treatment and provide destigmatized care through regular visits in an integrated care setting. We studied one family medicine, one behavioral health, and two SUD treatment organizations in rural counties with high SUD rates and limited resources that were funded to implement the model.</p> Methods <p>To examine the startup and early implementation phases of Nurture Oregon, we used a prospective, observational design to appreciate the effort from multiple perspectives. We observed program development meetings, team operations, and conducted semi-structured interviews with organization leaders, team members, and community partners. We used an inductive and comparative approach to identify sites’ startup and early implementation activities and challenges.</p> Results <p>Each site started with different program elements at baseline. This influenced the model elements each organization worked on during startup and the implementation challenges they experienced. The SUD and behavioral health organizations did not fully integrate care due to difficulty developing partnerships with medical organizations; they leveraged peers and doulas to provide cohesion for patients. The family medicine site was the only site that fully implemented the model, but they experienced barriers to financially supporting their peer workforce due to licensing and reimbursement policy constraints. All sites experienced challenges collaborating with hospital labor and delivery departments, and they all took steps to address patient housing needs by connecting patients to housing resources or acquiring housing units.</p> Conclusions <p>Implementing a care model to integrate medical and SUD treatment for pregnant individuals is difficult to accomplish but has the potential to make a significant difference in maternal and child health outcomes, recovery success, and prevention of foster care placement. Experiences during the startup and early implementation phases can shape the entire trajectory of a program and determine its long-term success. Our work shows the early challenges that need to be addressed to build an integrated program.</p>