Acquired risk factors are probably more common that congenital risk factors. However, the combination of congenital and acquired risk factors is likely to be the most dangerous for the development of VTE.

Changes in clinical practice have led to changing behaviour. For instance, the more active approach in the puerperium, with early mobilisation, and the use of prophylactic anticoagualation schemes have reduced the incidence of clinically overt VTE in several of the areas shown in the list.