Trophoblasts play an important role in the physiological changes of the spiral arteries as well in other processes during establishment of the placental vasculature, but together with trophoblasts, other cell types clearly are involved in the regulation of angiogenesis during pregnancy. Among them are decidual and placental macrophages as well as dendritic, endothelial, uNK, and mesenchymal cells. Many of these cells secrete or respond to angiogenic factors, such as members of the VEGF family [40, [47] [48] [49] [50] .