Fetal and neonatal alloimmune thrombocytopenia (AIT) is a serious disease that can affect subsequent siblings to an even greater degree than a first affected child. The devastating outcome of antenatal intracranial hemorrhage (ICH) is not uncommon. Great strides have been made in the antenatal diagnosis and treatment of this disease. This article reviews our knowledge of the laboratory diagnosis of AIT during pregnancy, the pitfalls in this diagnosis, the natural history of AIT during pregnancy, and the collected series of the management of fetal AIT in both Europe and the United States. Discrepancies in outcome between European and American studies exist. Reasons for these discrepancies are highlighted, including differences in populations studied, differences in management, and differences in the definition of response to treatment. Intravenous immune globulin appears to be efficacious in increasing the fetal platelet count and decreasing the occurrence of ICH.