Examining Site-Level and Structural Factors Influencing the Recruitment and Engagement of Participants of Color in Perinatal Substance Use Research: Insights From the Medication Treatment for Opioid Use Disorder in Expectant Mothers (MOMs) Trial

BACKGROUND: Racial and ethnic inequities persist in perinatal opioid use disorder (OUD) care, with pregnant and postpartum people of color facing structural barriers to using medications to treat OUD (MOUD). Because access to clinical research is often mediated through treatment settings, these structural barriers may also shape who is reached, recruited, and retained in perinatal OUD trials. The Medication Treatment for OUD in Expectant Mothers trial (NCT03918850) provided an opportunity to assess how site-level and policy contexts influenced equitable recruitment, including gaps between projected and actual enrollment. METHODS: We employed a convergent parallel mixed-methods design integrating thematic analysis of semi-structured qualitative interviews with non-White and/or Hispanic trial participants and research staff, site survey data, state policy classifications, and administrative enrollment data from the 13 trial sites. We examined how clinical structures, staffing composition, and policy environments shaped equitable recruitment. For each site, we calculated a recruitment ratio (actual/expected non-White and/or Hispanic enrollment). RESULTS: Among the 13 trial sites, 3 exceeded projected recruitment of non-White and/or Hispanic participants, 7 fell below projections, and 2 enrolled no non-White and/or Hispanic participants. Recruitment ratios (actual/expected) ranged from 0.0 to 6.3. Sites that exceeded projections commonly reported the inclusion of peer clinical staff and integration of prenatal and OUD care and were more often located in states without mandated reporting of MOUD during pregnancy. Qualitative analyses of participant (n = 17) and research staff interviews (n = 32) identified themes of trust, representation, and lived experience, emphasizing their importance for equitable recruitment and engagement. CONCLUSION: Equity in perinatal substance use disorder (SUD) research depends not only on inclusive trial design but also on the relational and policy conditions that build trust and enable participation. Beyond demographic targets, findings point to institutional practices, community partnerships, and supportive policy environments as actionable levers to promote equitable recruitment and engagement in perinatal SUD research.