PROJECT SUMMARY Maternal mental illness following childbirth is associated with substantial public health burden. Postpartum psychopathology is a leading contributor of maternal morbidity and mortality and can endanger the child’s wellbeing onward from birth. This suggests intergenerational effects. While efforts exist to reduce postpartum depression, childbirth-related posttraumatic stress disorder (CB-PTSD), a condition that affects 240,000 American women each year, is underdiagnosed and undertreated. The adversity of CB-PTSD is demonstrated by 1) the close temporal relationship between the onset of CB-PTSD symptoms and the birth of the infant, 2) the child themselves becoming an unfortunate, constant reminder of the trauma (childbirth), which can distance the mother from the child during an important time for the formation of mother-infant bonding instrumental for healthy child development. Symptoms of PTSD follow a distinct triggering event and early signs appear in the period after a traumatic experience, providing a unique opportunity for an intervention of targeted individuals during a critical window when treatment could avert the PTSD symptom trajectory. This means that at-risk individuals could be approached and screened in the hospital following childbirth and receive an early intervention to buffer CB-PTSD symptoms and optimize mother and child outcomes. In this randomized controlled trial (RCT), we identify individuals who have acute stress response in the hours following delivery indicative of risk for subsequent CB-PTSD. They will be randomized to take part in a brief expressive writing (EW) about their recent childbirth or about a neutral experience over 3 consecutive days starting from Day 5 postpartum (PP). We will then follow them at repeated time points, to assess immediate (Day 8 PP) and sustained (Mo. 2) treatment effects. Their infants will be studied at Mo. 2 PP to examine the influence of the intervention on the foundation of mother-infant bonding. Maternal CB-PTSD will be quantified using psychodiagnostic, psychometric, and psychophysiologic measures and mother-infant bonding using psychometrics and a behavioral observational assessment of mother-child interaction. This study will begin to fill the critical clinical gap in interventions to support maternal mental health following traumatic childbirth and enhance opportunities for maternal resilience and psychological growth. Establishing an effective intervention, may lead to the implementation of a safe, feasible, cost-effective therapy in hospital settings that is adherent to the special needs of mothers, thereby reducing the odds of developing a potentially preventable, costly, posttraumatic disorder and fostering healthy child development. In addition, the proposed study will further the NICHD missions that “women avoid harmful effects from reproductive processes and children achieve healthy and productive lives.”