Fetal/Neonatal Alloimmune Thrombocytopenia (FNAIT) is caused by destruction of fetal blood platelets due to maternal antibodies. This condition, which most commonly results from incompatibility between the mother and the fetus for the Human Platelet Antigen-1a (HPA-1a), may lead to intracranial hemorrhage, damage of the central nervous system (CNS) and even death of the fetus or the newborn. It can be the cause of strokes in term newborns. FNAIT is usually attributed to the presence of anti-HPA-1a antibodies. Its incidence rate is estimated at approximately 1/1000- 2000 live births. In the absence of a screening program, it is usually diagnosed after birth of a child with symptoms of thrombocytopenia or CNS hemorrhage. Monitoring of antibody production and thrombocytopenia treatment to effectively minimize the risk of stroke are therefore launched only at the next pregnancy. Testing indications are broader to include fetal ultrasound for symptoms of stroke to the CNS, ventricular enlargement or hydrocephalus, and obstetric failure. Diagnostic process is also recommended prior to the planned cordocentesis, in vitro fertilization and in sisters of mothers with children with FNAIT history. HPA-1a testing remains the best method for diagnosing pregnancies at risk. The detection frequency for FNAIT in Poland remains low Therefore, the Institute of Hematology and Transfusion Medicine (IHTM ) will have performed such HPA-1a antigen testing in 30000 Polish women within the framework of the PREVFNAIT program by March 2016. HPA-1a negative women (2% of the population) are a risk group for production of anti- HPA-1a antibodies responsible for FNAIT therefore all of them will be monitored for the presence and activity of anti-HPA-1a antibodies. Such testing will be performed free of charge for the women. The scientific goals related to the grant include 1) estimation of FNAIT prevalence in Poland and 2) search for biomarkers to predict the risk of the antibody production and severity of fetal thrombocytopenia.