PROJECT SUMMARY/ABSTRACT Congenital heart disease (CHD) is the most common congenital anomaly, affecting nearly 1 in 100 infants. Feeding is a primary area of concern for these infants, as feeding problems are associated with poor surgical and developmental outcomes and are often more concerning to families than the cardiac condition. Infants with single ventricle (SV) CHD undergo a series of 3 staged childhood surgeries and are at particularly high risk for feeding-related morbidity and mortality. Despite the key role feeding plays in outcomes for infants with SV CHD, research in this area is limited. Human milk feeding (parent’s own milk or donor human milk) and direct breastfeeding (human milk via a latch at the breast) have been identified as practices particularly in need of high-quality evidence to drive practice and policy. The strongest evidence supports exclusive human milk feeding as a life-saving intervention due to reduced risk for necrotizing enterocolitis. Direct breastfeeding supports cardiorespiratory stability during feeding, improves human milk feeding duration, and is preferred by most birthing persons. However, only 1 report of exclusive human milk feeding for infants with SV CHD exists (15% at stage 1 palliation surgery [S1P] discharge), and rates of direct breastfeeding are unknown. From the limited data, it appears these infants are far from the Healthy People 2030 objective of 42.4% exclusive breastfeeding through 6 months. The purpose of this study is to address the critical gap in knowledge about human milk feeding and direct breastfeeding for infants with SV CHD. Specifically, this study aims to: 1) Determine the prevalence of human milk feeding and direct breastfeeding for infants with SV CHD during the S1P hospitalization, at S1P discharge, and at stage 2 palliation surgery (S2P); 2) Identify factors that are positively and negatively associated with human milk feeding and direct breastfeeding at S1P discharge and at S2P; and 3) Estimate the effect size of human milk feeding and direct breastfeeding on key outcomes for infants with SV CHD, including necrotizing enterocolitis, postoperative complications, time to full feeding volume, length of stay, unplanned readmission, and mortality. The study aims will be accomplished through secondary analysis of a multisite registry (sample size ~2000) from the National Pediatric Cardiology Quality Improvement Collaborative (~60 sites), which consists of data from 2016–2021. At the completion of this study, we expect to have gained a clearer understanding of current rates of these feeding practices; identified supportive and limiting factors; and determined associations with key outcomes. This study is significant because it has the potential to inform much-needed clinical guidelines in this area, and could support our long- term research goal of developing culturally-responsive, family-centered interventions that improve the low rates of human milk feeding and direct breastfeedi...