Morphologic changes in the hypertensive placenta.

Pregnancy complicated by hypertension is commonly associated with placental insufficiency, thereby resulting in fetal growth retardation. Furthermore, reduced utero-placental blood flow has been recognized in cases of severe preeclampsia with hypertension. Thus, it must be assumed that histological as well as ultrastructural findings in hypertensive placentas are due to the occlusion or narrowing of the uteroplacental vasculature as well as placental ischemia. Microscopically, these placental changes include infarcts, increased syncytial knots, hypovascularity of the villi, cytotrophoblastic proliferation, thickening of the trophoblastic basement membrane, obliterative enlarged endothelial cells in the fetal capillaries and atherosis of the spiral arteries in the placental bed. In addition, ultrastructural features are characterized by a decreased number of syncytial microvilli, proliferation of cytotrophoblastic cells, focal syncytial necrosis, thickening of trophoblastic basement membrane and narrowing of the fetal capillaries, as a number of studies have demonstrated. These placental abnormalities can be seen not only in human toxemia, but also in animals with experimentally induced toxemia or with spontaneous toxemia.