European collaborative study of the antenatal management of feto-maternal alloimmune thrombocytopenia.

The aims of this study were to determine whether the severity of fetomaternal alloimmune thrombocytopenia (FMAIT) in the current pregnancy could be predicted from the history of FMAIT in previous pregnancies, and to assess the effects of different types of antenatal intervention. Fifty-six fetuses were studied that all had a sibling affected by FMAIT due to human platelet antigen 1a (HPA-1a) alloimmunization. Cases with a sibling history of antenatal intracranial haemorrhage (ICH) or severe thrombocytopenia (platelet counts of < 20 x 109/l) had significantly lower pretreatment platelet counts than cases whose siblings had less severe thrombocytopenia or postnatal ICH. Maternal therapy resulted in a platelet count exceeding 50 x 109/l in 67% of cases. None of the fetuses managed by serial platelet intrauterine transfusions (IUT) suffered ICH following treatment. However, several serious complications arose with fetal blood sampling (FBS). Overall, intervention improved outcome, as three study cases suffered from antenatal ICH and three others died whereas 15 study cases had a sibling with an ICH, eight of whom died. The results of this study suggest that the start of therapy can be stratified on the basis of the sibling history of FMAIT, and support the use of maternal therapy as first-line treatment.