Foetomaternal alloimmune thrombocytopenia is a syndrome where the foetus or neonate runs the risk of haemorrhage, in particular intracranial haemorrhage. The cause of thrombocytopenia is an antibody of class IgG formed in the mother due to paternal incompatibility. During the last three years of immunohaematological investigation of neonatal thrombocytopenia in 18 cases an alloimmune cause was proved and thus the diagnosis of foetomaternal alloimmune thrombocytopenia was confirmed. During the investigation period already two women were found who expected their second child running the risk of thrombocytopenia. In more than half the cases the cause was anti-HPA-1a antibody. The authors recommended and tested in practice a pattern for examination of neonatal thrombocytopenia where an important part is played by assessment of the HPA genotype of the child’s mother and father: it is possible to predict the level of foetal risk during a subsequent pregnancy. To protect neonates or foetuses running the risk of intracranial haemorrhage by administration of a suitable thrombocytic transfusion preparation a panel of donors with an assessed HPA genotype was assembled, comprising some 350 donors. So far these donors were used in three instances. In one case the thrombocyte transfusion preparation HPA-1bb was administered by the intrauterine rute.

        Key words: alloimmune thrombocytopenia, frequency of HPA genotypes, thrombocytic antibodies, antigen negative donors