Background: Thrombocytopenia is a frequent complication in high risk neonates. The platelet count is an important index of hemostasis in the newborn infants, but the platelet
number alone does not give a complete picture of platelet maturity and function.
The purpose of this study was to define further the entity of thrombocytopenia and the variation of platelet indices in the high risk neonates with regard to etiologic factors,
clinical features, and prognosis.
Method : Blood samples from umbilical or femoral vein collected in K2EDTA bottle of 125 high risk neonates were analysed with Coulter Hematology Analyser Model STKS.
Result :
1. In 125 high risk neonates, thrombocytopenia( < 100,000/μl) was associated with risk factors such as sepsis, low Apgar score, small for gestational age (p<0.01).
2. In 125 high risk neonates, the range(Mean±SD) for platelet count, mean platelet volume, plateletcrit, and platelet distribution width were 215.31 ± 134.24 ×
103/μl, 7.91±0.96 fl, 0.173±0.105 %, 17.20±0.87, respectively. Compared with normal ranges of full term neonate, PC and Pct were significantly lower than
normal ranges (p<0.05), but MPV and PDW were significantly higher than normal ranges (p<0.05).
3. High risk neonates with regard to risk factors were compared with normal full term neonates in platelet count and platelet indices, respectively.
In prematurity, respiratory distress syndrome and intracranial hemorrhage, PC and Pct were lower but MPV and PDW were higher than those in full term neonates (p<0.05).
In small for gestational age, neonatal hyperbilirubinemia, perinatal asphyxia, low Apgar score and hypoxic brain damage, PC and Pct were lower but PDW were higher than
those in full term neonates (p<0.05), but there was no significant difference in MPV(p>0.05).
In sepsis, PC and Pct were lower than those in full term neonates(p<0.05) but there were no significant differences in MPV and PDW(p>0.05).
4. In thrombocytopenic high risk neonates, MPV and PDW were significantly higher but Pct was significantly lower than normal range(p<0.05).
Conclusion: Various risk factors in the neonates affect the platelet count and platelet index, but it is difficult to interprete the result of my study, because risk factors of high risk group are overlapping.
But tendency of consumption or destruction of platelet rather than defective thrombopoiesis in most of risk factors is prominent.
This result may serve as a basis of differentiating pathogenesis or therapeutic consequence in thrombocytopenic neonates.

Keywords: Platelet count, Mean platelet volume, Plateletcrit, Platelet distribution width, High risk neonates,