'Normal' haemostasis parameters: a study in a well-defined inborn population of preterm infants.

Coagulation studies were performed in a well-defined inborn population of preterm neonates in cord blood and arterial blood obtained at age 48 h. Eighty infants fulfilled all the inclusion criteria. Our results show an increase in the hepatic vitamin K1 dependent and independent factors with postnatal age. The APTT became shorter, the factor II-VII-X, alpha 2-antiplasmin, plasminogen activities and fibrinogen level rose with increasing postnatal age. We found no change in the platelet parameters measured with postnatal age except that the megathrombocyte index was increased at age 48 h in infants less than 29 weeks gestation. There was little change with gestational age of any factors except the vitamin K1 dependent factors. Factor II-VII-X activity rose and the APTT became shorter with increasing gestational age. Many of the haemostasis results did not fall within the normal adult range. We discuss the significance of 'abnormal' and 'normal' results in preterm infants.