Brunst KJ, et al. - This study aims to investigate associations of maternal lifetime stress, current negative life events, and depressive and posttraumatic-stress-disorder symptom scores with placental mitochondrial DNA copy number (mtDNAcn) in a racially/ethnically diverse sample from the Programming of Intergenerational Stress Mechanisms (PRISM) study. These studies are first to link increased maternal psychosocial stress with decreased placental mtDNAcn and add to literature documenting racial/ethnic differences in the psychological sequelae of chronic stress that may contribute to maternal-fetal health.