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.