2.1 The relationship between thrombocytopenia and bleeding A complex relation exists between thrombocytopenia in preterm neonates and bleeding. This is illustrated by a recent observational study that demonstrated that only 9% of neonates with a very low platelet count developed major bleeding.(1) Moreover, patients with normal platelet counts bleed quite frequently, as evidenced by another study in which 25-38% of the patients with an IVH did not have thrombocytopenia.(2,3) Several recent reviews have highlighted that the fact that neonatal bleeding and neonatal thrombocytopenia often occur in the same timeframe, does not necessarily imply a causal relationship.(4,5) It is difficult to identify the role of thrombocytopenia in bleeding, because bleeding is a multifactorial process, and because there are a lot of interactions between bleeding, thrombocytopenia and clinical variables. Moreover, neonatal platelets appear to be different from adult platelets in many ways, which complicates our understanding of the effect of low platelet counts on bleeding risk, or the effect of transfusion of (adult) platelets in the neonatal system.(6)