Project Summary/Abstract Nearly 2 million women pass through U.S. jails each year, with nearly 8,000 admissions of pregnant people with opioid use disorder (OUD). Providing evidence-based treatment to these individuals is essential to addressing the opioid epidemic, to optimizing maternal and newborn outcomes, and to promoting maternal health equity. There is increasing recognition of the critical role of jails in providing access to medication treatment for opioid use disorder (MOUD) as a means of curbing the opioid epidemic, reducing overdose deaths, and promoting racial equity for a group of individuals who are systematically marginalized. While there is a growing number of jails that are expanding access to MOUD, strategies that are specific to the unique needs of pregnant people are lacking. Moreover, many jails still do not provide MOUD even in pregnancy, despite the well-established standard of care of avoiding withdrawal and the known benefits of MOUD specifically for pregnant individuals. Our long-term goal is to ensure that pregnant people with OUD in jails receive appropriate and timely care to optimize their long-term wellbeing and that of their infants. The overall objective is to develop and pilot an adaptable implementation strategy and toolkit for jails to be able to provide access to pregnancy-specific OUD care. The rationale is that jails vary tremendously in size, resources, and health care delivery systems, and need tools they can tailor to their environment. Ensuring jails provide access to MOUD, and in ways that are tailored to the distinctive medical, mental health and social structural aspects of care for pregnant people with OUD is essential for improving short and long-term pregnancy, recovery, and intergenerational outcomes. This project will engage multiple stakeholders, including directly impacted people, to design then pilot a patient-centered and jail-feasible implementation strategy that will facilitate and enhance jails’ implementation of MOUD for pregnant people. The strategy will contain a menu of tools to assist jails with immediate needs to provide MOUD to pregnant people entering jails; with pregnancy-tailored counseling; and with other support services and linkages to care that center the obstetrical, psychosocial, and structural needs of this population. The implementation strategy will also be adaptable to a variety of types and geographies of jails. They will then be piloted at four jails with different baseline capacities and services for MOUD for pregnant people. The steps proposed in this R34 are necessary for building the tools, outcome measures, and capacity that will be scaled-up in a future R01 hybrid implementation/effectiveness trial to improve OUD treatment access and maternal and infant health outcomes for this long-overlooked group.