Placental vascular dysfunction is a major cause of pregnancy complications, such as intrauterine growth restriction (IUGR). However, current knowledge on human placental vascular architecture is limited. In this study, for the first time, we characterized the structure of the placental vascular system ex-vivo, using MRI. Fifteen normal placentas and one with IUGR were studied using a novel method, and the vascular structure was analyzed with an automatic algorithm. Results provided information regarding: cord insertion location; branching pattern; branching generation; and daughter to mother diameters of normal placentas. Preliminary results from one IUGR placenta suggest significant differences from normal placentas.