Oral contraceptive therapy (OCT) is associated with a fourfold increase in the risk for venous thromboembolism (VTE). Women with congenital defects have a much higher risk. Because it is impossible to screen all women undergoing OCT, it is advisable to adopt some guidelines in an attempt to define the group of women who may be particularly exposed to the risk of VTE. On the basis of experience and that in the literature, two flow charts are used that are simple and reliable. The two flow charts are based on an accurate family and personal history so that an extensive investigation can be carried out only for women who show a positive family or personal history for idiopathic thrombosis. The definition of idiopathic thrombosis may be difficult, particularly in the case of family members. In case of doubt the thrombotic event should be considered as idiopathic. The two flow charts are not intended to eliminate the OCT-related VTE but represent only an attempt to decrease the prevalence of this complication.
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