Changes of expression of contractile proteins (alpha-actin and myosin of smooth muscle cell) and of collagen of IV type in stroma of human placental villi were studied at the diagnosed placental insufficiency (PI) in III trimester of pregnancy. The study revealed pronounced disturbances of expression of contractile proteins and collagen of IV type at PI. It is shown that in perivascular envelopes of vessels of stem and intermediate villi there is present a much greater amount of cells expressing smooth muscle actin and myosin. These cells are arranged by the denser concentric layers and more compactly than in norm and fill the intervascular space inside the villi. The width of perivascular envelopes of vessels is higher, while vascular lumens are lower than in norm. In terminal villi the capillary walls are thickened and the number of pericytes immunopositive against the smooth muscle cell alpha-actin and myosin as well as collagen of IV type is increased. The change of synthesis of the cytoskeletal contractile proteins and collagen of IV type is shown to lead to structural disturbances of villi of different types and of perivascular areas and vessels, which doubtlessly indicates their participation in pathogenesis of placental dysfunction and of disturbance of placental hemodynamics.