Figure 58-3 The fetal circulation demonstrating the major blood flow patterns and oxygen saturation values (circled numbers highlight percent saturation). Ao, aorta; DA, ductus arteriosus; DV, ductus venosus; IVC, inferior vena cava; Li, liver; Lu, lung; P, placenta; PA, pulmonary artery; PV, pulmonary vein; RA and LA, right and left atria; RHV and LHV, right and left hepatic veins; RV and LV, right and left ventricles; SVC, superior vena cava; UA, umbilical artery; UV, umbilical vein. (From Birnbach DJ, Gatt SP, Datta S [eds]: Textbook of Obstetric Anesthesia. New York, Churchill Livingstone, 2000, p 51.)