Placental barrier to coagulation factors: its relevance to the coagulation defect at birth and to haemorrhage in the newborn.

The placental barrier to coagulation factors was assessed by measuring their levels in maternal venous and neonatal umbilical arterial and venous blood and was found to be largely complete. Detailed coagulation assessments in a large number of term and premature neonates showed that term neonates had a mild coagulation deficiency at birth. Premature neonates had a more definite deficiency, which became more severe with increasing prematurity. Mortality in low birth weight premature infants was associated with a severe coagulation deficiency, and was frequently due to cerebral haemorrhage. It is suggested that the coagulation system of low birth weight infants should be assessed to enable prophylactic treatment of those with a severe deficiency.