Schematic of events occurring at the decidual/trophoblast interface, comparing mouse (left) and human (right). In the mouse, the decidua, which does not normally express IGFBP-1, and the layers of the placenta are shown. In the human decidua, IGFBP-1 is normally expressed in high abundance and is positioned to regulate extravillous trophoblast invasion into this compartment (see text).