A lupus anticoagulant in pregnancy has almost always been associated with an adverse outcome. In previous reports of successful pregnancy in patients with a lupus anticoagulant, whether treated or untreated, all were complicated by premature delivery, and many were complicated by preeclampsia or placental insufficiency. Four patients with systemic lupus erythematosus and an untreated lupus anticoagulant, had an uncomplicated pregnancy that resulted in a live birth at term. The circulating anticoagulant persisted throughout the pregnancy in three patients, and disappeared spontaneously during pregnancy in the fourth patient. As pregnancy outcome is unpredictable, the best treatment of these patients remains to be determined by controlled studies.