Hb Bart's Hydrops Fetalis Syndrome (BHFS) resulting from α0-thalassemia is considered a universally fatal disorder. However, over the last three decades improvements in intrauterine interventions and perinatal intensive care have resulted in increasing numbers of BHFS survivors. We have initiated an international registry containing information on 69 patients, of which 31 are previously unpublished. In this perspective we analyze the available clinical information to document the natural history of BHFS. In future, once we have accrued sufficient cases, we aim to build on this study and provide information to allow counseling of at-risk couples. To date 39 patients have survived beyond the age of 5 years, 18 of whom are now older than 10 years. Based on the available cases we find evidence to suggest that intrauterine therapy provides benefits during the perinatal and neonatal period, however, it may not provide additional benefits to long-term growth and neurodevelopmental outcomes. Growth retardation is a major adverse long-term outcome among BHFS patients with ~40% being severely affected in terms of weight and ~50% in terms of height. There is also an increased risk of neurodevelopmental delay as we find 20% (11/55) of BHFS survivors suffer from a serious delay of ≥6 months. Most patients in the registry require lifelong transfusion and often have associated congenital abnormalities and co-morbidities. This perspective is a first step in gathering information to allow provision of informed counseling on the predicted outcomes of affected babies
