The most important agent of human malaria, Plasmodium falciparum, is responsible for pathological changes in different organs, including the placenta. Although the parasitemia in the intervillous spaces of the placenta may be very pronounced, species of Plasmodium usually do not cross the placental barrier, and only a few cases of true congenital malaria have been reported. Placental ma-larial changes are restricted to the intervillous spaces and the villous surface, with few or no modificationS in the deepervillous structures. In this work, the authors describe the histological and ultrastructural changes in the placenta and attempt to correlate these lesions with modern path-ophysiological concepts of malaria. The placentas examined were from women living in an equatorial region with a high malarial concentration. Lesions were present in 247 specimens (33 per cent) of the collected placentas. All but 10 of those with malarial changes were at term. The weight of the 237 malariainfected placentas at term ranged from 200–720 g, with a mean of 388+ 82 g. The mean weight of a control group without histological modifications (N= 374) was 434 t 80 g. The mean difference of 46 g was highly significant (P< 0001).

All of the placentas were characterized by some combination of parasitemia, macrophage infiltration, malarial pigment deposits, syncytiotrophoblastic necrosis, and tro-phoblastic basement membrane thickening. There was no difference between the mature and immature placentas in the severity of placental malarial changes. Malarial parasites were recognized in H & E-stained placental sections in 108 cases (42 per cent). They were located in maternal erythrocytes and/or in maternal mac-rophages, but never in fetal erythrocytes or villous struc-tures. All intraerythrocytic maturational stages were present, but the trophozoite form predominated. The parasite number varied from one parasite (or less) per high-power