The pathogenesis of perinatal death [in humans] due to placental infarction was analyzed in a large prospective study that included more than 1000 medical, demographic, hereditary and postmortem variable. The disorder was the 5th most frequent casue of death in the study with a perinatal mortality of 2.26/1000 births. Its frequency was directly correlated with the gravidas'' blood pressures, an effect augmented by albuminuria and work during pregnancy. Fatal infarcts were increased 20-fold with glomerulonephritis, 5-fold with abruptio placentae and 2-fold when the gravidas'' Hb were over 12 g/100 ml. Maternal weight gains were suboptimal and the involved neonates had a pattern of growth retardation characteristic of undernutrition. The disorder was more frequent when the gravida had made few prenatal visits for medical care and had had prior unsuccessful pregnancies.