The Effect of the Mini-pill on Blood Factors in Women at Increased Risk for Forming Blood Clots

Inclusion Criteria: * Women with a history of venous thromboembolism (VTE, blood clot in a vein) and women with a history of blood tests which demonstrate an increased risk of thrombosis who desire contraception. * Blood tests which demonstrate an increased risk of thrombosis include the following: * Hyperhomocysteinemia/MTHFR mutation * Prothrombin gene mutation * Factor V Leiden heterozygotes * Factor V Leiden homozygotes, antithrombin III mutation * Protein S deficiency and Protein C deficiency. Exclusion Criteria: * Women on current anticoagulation therapy * Women with a history of oral contraceptive related thrombotic events * Active or history of cigarette smoking within the past 6 months * Pregnancy * Active lactation * Known hypersensitivity to progestin * Any history of malignancy * History within the last three months of surgery or planning surgery during the study period * Undiagnosed vaginal bleeding * Active liver disease and history within the last 5 years of alcoholism or drug abuse. * Additionally, women must be greater than 3 months postpartum and have had two months without contraceptive hormones (such as the birth control pill) and 6 months without Depo-Provera use prior to enrollment.