PROJECT SUMMARY While newborn screening (NBS) programs have prevented death and disability for scores of children with inherited disorders over the past 50 years, these programs face significant emerging challenges. Specifically, the NBS system has ushered in an era in which increasing numbers of parents are leaving the NBS experience uncertain about their child's future health. This erosion of prognostic certainty stems from the addition of disorders to NBS panels that have broad phenotypic variability. As a result, a new group of children called “patients in waiting” are literally waiting to see when – or if – they develop signs and symptoms of disease. While society mandates that these children be screened, we have little understanding of the benefits and harms of these uncertain prognoses. Previous studies have provided vital foundational work on the potential harms and benefits for “patients in waiting;” however, little quantitative and no longitudinal population-based data exist to inform our care for these children. This gap has significant ethical and policy implications. From an ethical perspective, it leaves us unsure of the balance of benefits and harms for children who undergo a mandatory public health program days after birth. From a policy perspective, it leads to the addition of disorders to mandatory state NBS panel based on incomplete data. The proposed project’s overall objective is to close this gap by examining the scope and magnitude of benefits and harms on parents and their children who receive an uncertain prognosis after NBS. We will accomplish the project objective through a longitudinal multistate cohort study of parents of “patients in waiting,” with the following aims: 1) To determine the longitudinal scope and magnitude of benefits and harms on parents and their children who have received an uncertain prognosis after NBS; 2) To elucidate the longitudinal experiences of parents and their children who have received an uncertain prognosis after NBS; 3) To develop recommendations for NBS programs that will inform policies and practices to maximize benefit and minimize harm to children who receive an uncertain prognosis after NBS. In summary, this project will provide the most comprehensive assessment to date of the benefits and harms of an uncertain prognosis after NBS and ensure that children and their parents continue to receive a net benefit from this successful public health program.