A point mutation (G20210A) in the Factor II (prothrombin) gene is the second most common cause of inherited blood clots and accounts for 20% of the inherited blood clotting disorders. The incidence of this mutation in the Caucasian population is 1-2% and in African Americans it is 0.1%. Carriers of this mutation have an increased risk (3x) of developing a blood clot in the deep veins (deep venous thrombosis or DVT). A test for this mutation is usually only recommended if there is a family history of blood clots (DVT) or in cases where the cause of the blood clot is not clear or in pregnant women with recurrent miscarriages. A more common cause of a blood clotting disorder that is inherited from the parents is the Factor V Leiden mutation.