Transplacental Foetal Blood Loss: A Common Event

In 1941 Levine and his colleagues postulated that the way in which Rh sensitization occurred in Rh negative mothers was by transplacental passage of Rh-positive foetal erythrocytes into the maternal circulation. At that time there were no available tech' niques for proving this hypothesis, and it was not known when the foetal cells entered the maternal circulation, nor how much foetal blood was required to stimulate Rh anti* body formation. Weiner (1948) and Wickster (1952) both postulated that a large foetal haemorrhage into the maternal circulation could cause anaemia in the newborn baby-Chown (1954) was subsequently able to prove beyond all doubt that a large foetc maternal transfusion could occur; after the birth of an anaemic baby, he was able to demonstrate the presence of both foetal erythrocytes (by differential agglutination) an<j foetal haemoglobin in the maternal blood. Furthermore he demonstrated materia1 antibodies against the foetal erythrocytes 3 weeks after delivery. After Chown's obsef vations further instances of large foeto-maternal transfusions were recorded, but the emphasis at this time appeared to be on detecting large rather than small foeta' haemorrhages. In 1957 Kleihauer, Braun and Betke evolved a method for differentiating erythr0' cytes containing adult haemoglobin from those containing foetal haemoglobin. Briefly they found that by fixing thin smears of normal adult and cord blood with methyl alcohol, and then treating the slides in a citric acid-phosphate buffer at pH 3*4, the denatured haemoglobin from adult erythrocytes was soluble and this left the cel'i whereas denatured foetal haemoglobin was insoluble and remained within the cell-When haemoglobin stains were employed cells containing foetal haemoglobin stained up fully but cells which had contained adult haemoglobin appeared as "ghosts", only the cell outline being visible. This method, when applied to maternal blood, is extreme' ly sensitive for detecting any foetal erythrocytes that may be present, and since its original description further instances of large foeto-maternal transfusions haVg appeared in the literature. Using this technique Zipursky and his colleagues in Canada (1959) examined the blood of 42 mothers within 6 days of parturition, and found small numbers of foetal cells in 11, thus indicating the occurrence of small foeto' maternal transfusions. This opened the field for more intensive observations as to the incidence of these micro-transfusions from foetus to mother. Large series frotf Liverpool, Bristol, Inverness, Germany and Canada have shown that when maternal blood is examined within 2 days of delivery, foetal cells …