[Oral contraceptive pill and thrombotic risk: epidemiological studies]

The venous thromboembolism (VTE) is a rare event during childbearing age and during the assumption of combined oral contraceptive. The absolute risk of VTE in users of combined oral contraceptives is 20-30 per 100000 women years. A number of case-control studies published in recent years have shown an apparent increase in the risk of VTE among users of oral contraceptives (OCs) containing desogestrel, gestodene, drospirenone and cyproterone, relative to the use of levonorgestrel. The data derived from these recent studies is of borderline statistical significance because any important factors are not considered to evaluate the real correlation between the assumption of OCs and risk of venous thromboembolism. Among the factors that should be considered, there are: EE dose, duration of use, coexistance of other risk factors of venous thromboembolism (age, BMI, familiarity, surgical interventions) and other prescription bias. The lack of these factors is likely to contribute to the increased risk of venous thromboembolism observed in users of third-generation OCs when compared to that in users of second-generation OCs. To date, because of the inadequacy of epidemiological studies, the data about the correlation between OCs and TVE, are not conclusive and it will be necessary to carry out other studies to clarify this debating point, definitively.