Developmental Haemostasis

The haemostatic (blood clotting) system involves the interaction of proteins in the blood, the blood vessel wall and the flow of blood to control bleeding and blood clotting. Developmental Haemostasis is a term that represents the maturation of the haemostatic system from birth to adulthood. There are differences in the concentration, structure and activity of many proteins involved in blood clotting. These changes play an important role in physiological development and are important in providing appropriate diagnosis and treatment of bleeding and clotting disorders (e.g. thrombosis). The age-specific differences in the blood clotting system may contribute to the fact that children are less prone to developing thrombosis compared to adults.
Differences in structure of haemostatic proteins.
Studies have shown that there are structural differences in some of the major blood clotting proteins in newborns and children when compared to adults. These structural differences can lead to differences in the activity of haemostatic proteins within the blood clotting system, as well as other physiological systems (e.g. immune system).
Some examples of age-specific differences in the structure of blood clotting proteins are:
Implications.
Reference ranges demonstrate the normal test values for a healthy population. Diseases and disorders are diagnosed when a test value is outside the reference range. Many laboratories compare paediatric results to adult reference ranges or to published paediatric reference ranges that may not be specific for the test used. This can lead to misdiagnosis or over-diagnosis of blood clotting disorders as many proteins exist at levels during stages of infancy that would be associated with disease in adults. This can lead to unnecessary stress for families and can have significant medical implications for the child (e.g. further testing). 
The differences in the haemostatic proteins can lead to different interactions with anticoagulant drugs that are used to prevent and treat thrombosis in children. More studies are required to determine the optimal treatment strategies and doses of anticoagulants in children.
The role of developmental haemostasis in normal physiology is still not fully understood. It has been observed that the newborn haemostatic system is protective and contributes to a decreased risk of bleeding or thrombosis compared to adults. The differences may also be due to the role haemostatic proteins play within other physiological systems.