Introduction:Pregnant individuals with substance use disorders face complex issues that may serve as barriers to treatment entry and retention. Several professional organizations have established recommendations on comprehensive, collaborative approaches to treatment to meet the needs of this population, but information on real-world application is lacking. Sites participating in the NIDA CTN0080 “Medication treatment for Opioid use disorder in expectant Mothers (MOMs)”—a randomized clinical trial of extended release compared to sublingual buprenorphine among pregnant and postpartum individuals (PPI)—were selected, in part, because they have a collaborative approach to treating PPI with opioid use disorder (OUD). However, organizational differences among sites and how they implement expert recommendations for collaborative care could impact study outcomes.Methods:Prior to study launch at each of the 13 MOMs sites, investigators used the Pregnancy and Addiction Services Assessment (PAASA) to collect information about organizational factors. Input from a team of addiction, perinatal, and economic evaluation experts guided the development of the PAASA. Investigators programmed the PAASA into a web-based data system and summarized the resultant site data using descriptive statistics.Results:Study sites represented four US census regions. Most sites were specialty obstetrics & gynecology (OB/ GYN) programs providing OUD services (n= 9, 69.2 %), were affiliated with an academic institution (n= 11, 84.6 %), and prescribed buprenorphine in an ambulatory/outpatient setting (n = 11, 84.6 %); all sites offered access to naloxone. Sites reported that their population was primarily White, utilized public insurance, and faced numerous psychosocial barriers to treatment. Although all sites offered many services recommended by expert consensus groups, they varied in how they coordinated these services.Conclusions:By providing the organizational characteristics of sites participating in the MOMs study, this report assists in filling the current gap in knowledge regarding similar programs providing services to PPI with OUD. Collaborative care programs such as those participating in MOMs are uniquely positioned to participate in research to determine the most effective models of care and to determine how research can be integrated into those clinical care settings.