ABSTRACT Postpartum mood disorders (PPMD) affect 8-13% of new mothers, with another 16-23% experiencing elevated symptomology throughout the infant’s first year of life. A variety of interventions for PPMD exist, including pharmacological and psychosocial treatments such as social support. However, existing research on advantages of social support programs has been limited to the postpartum period only. As such, benefits of social support programs during pregnancy have not been established, and little is known about the conditions under which these programs may affect PPMD. CenteringPregnancy is a group-based prenatal care model with demonstrated positive maternal and infant health outcomes when compared to prenatal care-as-usual (CAU). It addresses many barriers commonly impeding prenatal mental health interventions, is a low-cost and easily disseminated model, and has high patient satisfaction across diverse samples. However, documented outcomes are limited to birth outcomes (e.g., reduced preterm birth rates, reduced low birth-weight, increased breastfeeding) and prenatal maternal physical health such as gestational diabetes and smoking. The research examining the effect on postpartum mental health is scant and limited by small sample sizes, absence of postpartum mental health assessments, and narrow operationalization of mental health outcomes (e.g., depression only). The proposed project will address these limitations by examining mental health benefits through the following Aims: 1) Use a pre-existing dataset to determine under what conditions the CenteringPregnancy model versus CAU affects maternal depression outcomes; 2) Gather new data to examine impacts as a clinical intervention on relevant maternal outcomes (e.g., PPMD; interaction effects of PPMD and early parenting), while simultaneously observing and gathering information on implementation in order to a) maximize clinical efficacy utility (i.e., focusing on internal validity), and examine b) clinical effectiveness (i.e., generalizability), and c) implementation outcomes (i.e., acceptability, feasibility) in order to facilitate sustainability and scalability as an effective intervention and prevention strategy for PPMD; and 3) Strengthen our research environment and engage undergraduate students in collaborative research while mentoring and instructing them in research concepts and processes (e.g., research methodology, participant recruitment, ethical and professional standards, data collection and analysis, and scholarly productivity) as they relate to the CenteringPregnancy model, maternal mental health, and relevant outcomes. The results of this research will contribute to the existing knowledge base by advancing understanding of social support interventions relevant to maternal mental health and revealing targeted points of entry for prevention and intervention programs to alter maternal mood disorder risk during pregnancy and throughout the postpartum period. Further, the focu...