In more than half of the couples with recurrent miscarriage, no underlying cause can be found. Both acquired and hereditary risk factors for venous thrombosis, i.e. thrombophilia, constitute an aetiologic factor in a minority of patients with recurrent miscarriage. In women with a diagnosis of antiphospholipid antibody syndrome, treatment with low-dose acetylsalicylic acid and low-molecular-weight heparin has been shown by a valid randomised controlled trial to improve the results of a subsequent pregnancy. However, it is unknown whether anticoagulant treatment of women with recurrent miscarriage and hereditary risk factors for thrombophilia improves the outcome of a subsequent pregnancy.