Fetomaternal blood group incompatibility studies in placental intervillous thrombosis.

Samples of maternal and fetal blood from 32 cases of placental intervillous thrombosis have been analysed for blood group incompatibility and compared to a control group of 21 cases. No overall link has been demonstrated between intervillous thrombosis and ABO incompatibility. Red cell antibody reactions of all types probably account for only a small proportion of thrombi and it is suggested that the principle mechanism may be a thromboplastin release from the damaged vasculo-syncytial membrane, causing a coagulation of the mixed maternal and fetal cells.