IntroductionLimited research has examined participant subgroups enrolled in postpartum depression interventions. Via a cluster-randomized trial of the Mothers and Babies (MB) postpartum depression preventive intervention, we examined changes in depressive symptoms across pre-specified participant subgroups: race/ethnicity, first-time mother, language of intervention receipt, and client education. We also examined interaction effects between subgroups and study arm (usual care vs. intervention) o