Thrombocytopenia in the newborn.

Thrombocytopenia is the most common hemostatic abnormality in sick newborn infants. Although many conditions may be associated with neonatal thrombocytopenia, low platelet counts in the first few days of life are often caused by fetomaternal problems, whereas thrombocytopenia developing after the third day is usually secondary to sepsis or necrotizing enterocolitis. Despite the frequency of thrombocytopenia in sick neonates, the underlying kinetic mechanisms are not always clear. The commonly accepted theories of decreased platelet production or increased consumption are being scrutinized in the light of new evidence. Thrombopoietin and interleukin-11 are being investigated to unravel the complex pathophysiology of thrombocytopenia in neonates and they are also being explored as potential therapeutic agents. Guidelines for platelet transfusions continue to be variable and controversial.