Prenatal Diagnosis of a Rare Congenital Right Subclavian Artery–Superior Vena Cava Fistula

The right subclavian artery (RSA)–superior vena cava (SVC) fistula represents a rare arteriovenous fistula characterized by abnormal vascular channels connecting the arterial and venous systems. This report describes the first prenatal diagnosis of an RSA–SVC fistula. Differentiation from supracardiac total anomalous pulmonary venous connection (TAPVC) is challenging; however, three indirect indicators may aid differentiation: simultaneous dilation of the innominate artery and SVC, bi‐directional flow within the aortic arch, and a bi‐phasic, unidirectional, spiculated flow pattern at the confluence. Timely prenatal diagnosis serves as a vital tool for clinicians and families, paving the way for timely postpartum interventions while significantly enhancing postnatal prognoses.