Figure 58-1 A, Venogram in a term patient in the supine position before cesarean section. Radiopaque dye injected into the femoral veins fails to reach the inferior vena cava (IVC) but reaches the paravertebral veins. B, After cesarean section, blood is seen in the IVC. (From Kerr MG, Scott DB, Samuel E: Studies of the inferior vena cava in late pregnancy. BMJ 1:532, 1964.)