PIP: Low-dose oral contraceptives when tested for vascular or thrombotic effects not only show no risk of venous thromboembolic disease, but this method could possibly reduce the chance of thromboembolic disease as compared with pills which have a higher estrogen dose. It has also been found that pills containing lower doses of estrogen have no effect on the coagulatory system. Concerns raised about the connection between oral contraceptive use and the risk of cardiovascular disease called for testing in the late 1960s. Epidemiological studies confirmed the risk of oral contraceptive use and cardiovascular disease especially venous thromboembolism. A further association was identified between the amount of estrogens contained in oral contraceptives and the risk of disease. Estrogens affect the hemostatic system; decreases in antithrombin III activity in addition to platelet adhesiveness and blood viscosity have been observed in oral contraceptive users. Although both a decreased influence on the hemostatic system and the risk of thromboembolic disease have been found in pills with lower doses of estrogen, further research on the effect of the clotting system by low-dose oral contraceptives is needed.