PROJECT SUMMARY Congenital heart disease (CHD) is the most common birth defect. CHD affects all racial, ethnic, and socioeconomic groups, yet underserved populations (e.g., low-income Black and Hispanic patients) are disproportionally affected by disease-related morbidities. They are more likely to be delivered preterm, to be readmitted to the hospital after surgery, to exhibit developmental delays, and ultimately, to die from CHD. CHD is increasingly diagnosed prenatally across racial/ethnic groups. While prenatal diagnosis can be beneficial for the infant in that it facilitates medical care immediately following birth, mothers describe their prenatal experiences as highly stressful and traumatic. Maternal stress during pregnancy exerts a powerful influence on birth outcomes and developmental trajectories, particularly for children in underserved populations. Targeted efforts to mitigate impacts of maternal stress for this highly vulnerable population are lacking. In partnership with diverse parent and clinician stakeholders, our team designed HeartPREP, an innovative, virtually-delivered psychosocial intervention for mothers expecting a baby with CHD. HeartPREP will be delivered in English and Spanish through the Nemours App, an accessible tool for telehealth, education, and communication with clinicians. The proposed study will evaluate whether HeartPREP improves maternal and family outcomes following prenatal diagnosis of CHD. Participants across all study aims will be diverse expectant mothers carrying a fetus identified as having CHD, recruited from two hospitals within the Nemours Children’s Health System. We have assembled a team of experts in family-based psychosocial intervention and patient-centered outcomes research to (Aim 1) refine HeartPREP through Think Aloud Testing with 15-20 expectant mothers and evaluate initial feasibility, usability, and acceptability through beta testing with 10 expectant mothers, (Aim 2) determine whether HeartPREP modules produce clinically significant improvements on outcomes (emotional distress, social isolation, parenting self-efficacy, and hope; measured by PROMIS) in 20 expectant mothers (Proof-of- Concept), and (Aim 3) evaluate the impact of HeartPREP compared to standard care control (SCC). Sixty expectant mothers carrying a fetus identified as having CHD will be randomized to HeartPREP or SCC and will complete assessment of outcomes weekly during intervention (emotional distress, social isolation, parenting self-efficacy, and hope) and at post-intervention and 3-month postnatal follow-up (anxiety, depression, traumatic stress, and couple/family functioning). An R01 application planned for Year 2 would fund expansion of Aim 3 into a multi-site efficacy trial. HeartPREP has the potential to improve the emotional wellbeing of mothers expecting a baby with CHD, thereby altering developmental trajectories for this large population of children. This model can then be adapted for other birth defects (3% ...