Identification of erythrocytes in intervillous thrombi: a study using immunoperoxidase identification of hemoglobins

The origin of the erythrocytes in intervillous thrombi has never been definitively established. Fetal hemoglobin-containing erythrocytes were identified in histologic sections of intervillous thrombi using the peroxidase-antiperoxidase unlabeled antibody method. In 85 per cent of intervillous thrombi containing well-preserved erythrocytes, fetal hemoglobin-containing cells were found in quantities well in excess of the number seen in maternal blood. This definitely demonstrates the presence of erythrocytes of fetal origin in intervillous thrombi. Possible pathogenic mechanisms of intervillous thrombosis and fetal-maternal hemorrhage are discussed.