The placenta’s primary role is to provide for physiological exchange between the fetal and maternal systems (Meschia, 1983; Reynolds & Redmer, 1995). In this context, the importance of the placental circulation to successful pregnancy is exemplified by the close relationships among fetalweight, placentalsize, and uterine and umbilicalblood flows during normal pregnancies in many mammalian species (Reynoldset al.2005a,b).