Tentative guidelines and practical suggestions to avoid venous thromboembolism during oral contraceptive therapy

Changes in prescription patterns of oral contraceptives in a northern Italian province: relation with venous thromboembolism

Oral contraceptives (OC) are a definite risk for venous thrombosis. It is commonly accepted that they cause a fourfold increased risk of thrombosis compared to non-users. The prescription patterns were evaluated from 1990 to 2000 in a northern Italian province (province of Padua). This province is typical of other northern Italian provinces. As a consequence, it can be safely assumed that the observations gathered may apply to the entire north of Italy. During these years, a sharp increase in the use of OC was noted. Furthermore, around 1995 to 1996, a marked switch toward the use of preparations containing third-generation progestins was noted. During the past few years of the observation period, approximately 80% of women use preparations containing third-generation progestins. During the same period, an increased incidence of episodes of venous thromboembolism (VTE) was noted. The increase in the prevalence of VTE episodes appeared to be proportional to the increased use of OC, regardless of the type of progestin contained in the oral contraceptive preparations.

Proposal of a flow chart for thrombosis-free oral contraceptive therapy

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.