[Composition of intervillous thrombi from maternal and fetal blood].

In serological studies blood groups of intervillous thrombi of the placenta were identical with maternal blood groups in 88.9%. Identity with fetal blood groups occurred in 11.1%. Utilizing an elution technique in smears prepared from intervillous thrombi, 11.68% of the erythrocytes were of fetal, 88.32% of maternal origin. In conclusion, intervillous thrombi are mainly composed of maternal cells. The existence of small amounts of fetal cells simultaneously, points to the possible etiology: Local damage of the trophoblastic epithelium of the villi is followed by escape of fetal cells into the intervillous space and later aggregation of maternal blood. Finally, the clinical relevance of intervillous thrombosis in maternal Rh-isoimmunization, pregnancy induced hypertension and intrauterine fetal anaemia is discussed.