Fig. 2

Bifurcation of the ascending aorta and a complete vascular ring of the DAA on fetal echocardiography. a Left ventricular outflow tract view: The distal ascending aorta bifurcation is confirmed as the right arch and left arch. b Three-vessel tracheal view: A bifurcation of the ascending aorta into the right aortic arch and left aortic arch to form a complete O-shaped ring encircling the trachea, together with a number 9 configuration connecting with the left-sided ductus arteriosus. Both aortic arches demonstrate antegrade blood flow (AO or AAO: ascending aorta; R: right aortic arch; L: left aortic arch; PA: pulmonary artery; DA: ductus arteriosus; T: trachea)