Lupus anticoagulants are associated with venous and arterial thrombosis and with recurrent spontaneous abortion resulting from placental infarction. Treatment with high-dose prednisone and aspirin has been reported to reduce the otherwise very high frequency of spontaneous abortion in affected women. We report the case of a young woman with an idiopathic lupus anticoagulant who had a history of arterial and venous thrombosis and of previous spontaneous abortion; anticoagulation throughout pregnancy was associated with normal fetal growth and with an absence of placental infarction. We conclude that anticoagulation without concurrent prednisone or aspirin may provide an alternative approach to prevention of habitual abortion in some women with lupus anticoagulants.