The ultrasonography enables visualization of placental changes, including calcifications, placental lakes, indentations of the chorionic plate, and changes in gray-scale echogenicity. The ultrasonography also helps to identify abnormal position, abruption, hematoma and accreta. This capability is especially helpful in evaluating membranes and other anatomical relationships in twin gestations.Visualization of the continuity and curvature of structures of the placenta are more easily accomplished with 3D ultrasonography over 2D ultrasonography.