Transplacental Passage of Red Cells in Man

THE purpose of this communication is to report the results of an investigation into the frequency and magnitude of haemorrhage from the fœtal to the maternal circulation in a random series of deliveries. The total separation of the maternal and fœtal circulations was a long-held biological belief, and was only first seriously questioned in 1941, when the mechanism of haemolytic disease of the newborn was elucidated and Levine1 showed that Rh iso-immunization occurred less often than expected in ABO incompatible matings. Because of these Rh findings, it was postulated that the antigen was carried across the placenta into the maternal circulation by intact erythrocytes.