Thrombocytopenia is one of the common hematological problem encountered in the neonatal period particularly in sick newborns, premature babies and neonates admitted in neonatal intensive care units and usually indicates an underlying pathologic process. Platelet count and mean platelet volume in the newborn are similar to those in adults and in children and ranges from 150,000/uL to 450,000/uL and 7.5/fl respectively. They are 14 times smaller than erythrocytes. However, premature infants on an average have slightly lower platelet count than full term infants but practically within normal range. Fetal platelet count increases linearly with the gestation from mean of 187,000/uL at 15 weeks to 274,000/uL at 40 weeks. Postnatally, mean platelet volume increase slightly, over the first 2 weeks of life concomitant with an increase in platelet count. Platelet survival in newborn are not likely to differ significantly from those in adults i.e. 7-10 days (1-9).

Thrombocytopenia in newborns:

Thrombocytopenia is defined as platelet count less than 150,000/uL and platelet count less than 100,000/uL is considered as definitely abnormal at any gestational age and deserves further evaluation. However, significance of platelet count between 100,000 to 150,000/uL in neonate is not clear but needs further follow-up (6,7,8,10,11). Further investigations depend upon infant's condition and subsequent platelet count.

Incidence of thrombocytopenia in neonates

The incidence of neonatal thrombocytopenia varies depending upon: -

• Definition of thrombocytopenia < 1,00,000/cmm Vs 1,50,000/cmm.
• Timing of neonatal platelet count.

• Fetal and neonatal megakaryocytes are smaller and have lower ploidy than megakaryocytes of adult and hence may produce fewer platelets.
• Inadequate production of thrombopoietin in response to thrombocytopenia in neonates as compared to adult leading to limited ability to increase platelet production in response to increased platelet consumption.
• Thrombocytopenic premature neonates have fewer circulating megakaryocytes progenitors than do their non-thrombocytopenic counterparts (10,16,21,22,23).