Fetal echocardiograms were performed (Acuson Sequoia C256/Siemens Medical Solutions, Acuson Ultrasound Department, Mountain View, California) using a 6C2, 8C4 or 5V2c probe and persistence of the LSVC documented from routine views of the four chambers and transverse arch (the three vessel view). Postnatal diagnosis was confirmed by echocardiogram, at surgery, or at necropsy.