[Prenatal management of fetuses with alloimmune thrombocytopenia]

Fetal alloimmune thrombocytopenia is caused by maternal immunization against a fetal platelet alloantigen and transplacental transfer of the antibody into the fetal circulation. Since 10-20% of the fetuses or newborns are threatened by intracranial hemorrhages (ICH) early management is required. Intensive prenatal monitoring should be performed if a maternal HPA-1a antibody is known and a previous infant suffered from thrombocytopenia and/or ICH. Fetal blood sampling (FBS) should be started at 20th to 22nd weeks of gestation to assess fetal phenotype and platelet count. Different concepts to elevate the fetal platelet count have been discussed: corticosteroids, maternal intravenous immunoglobulins (ivIgG), fetal ivIgG and repeated fetal platelet transfusions. In a European survey with data from five centres maternal corticoid treatment and ivIgG infusion were accompanied by increasing fetal platelet counts in only 20 and 24% of the cases, respectively. In fetuses with very low platelet counts only transfusions of compatible platelets in short intervals are able to sustain a safe platelet count. Fetuses with mild thrombocytopenia should be monitored by subsequent FBS since it could be shown that platelet counts tend to decline during gestation. To avoid bleeding complications during and after FBS which was observed in about 5% of the cases every cord vessel puncture should be covered by a platelet transfusion. As no safe and non-invasive therapy exists for fetal alloimmune thrombocytopenia the value of prenatal screening programs in unaffected pregnancies is questionable.