Pregnancy loss, often recurrent, is one of the most important clinical manifestations associated with the primary antiphospholipid syndrome. In these cases, pregnancy wastage is related to the presence of antiphospholipid antibodies, namely lupus anticoagulant and anticardiolipin antibodies, but patients do not have features of systemic lupus erythematosus or any other well-defined autoimmune disease. We report here on the outcome of 21 consecutive pregnancies in 18 patients with the syndrome who were treated with low-dose aspirin (100 mg/day) from 1 month before attempting conception and throughout the pregnancy. Low-dose prednisone (15-30 mg/day) was added for potentially non-obstetric (autoimmune-related) reasons in six pregnancies. Patients were monitored as having high-risk pregnancies. Prior to therapy, the rate of live-born babies was 6.1% (46 previous fetal losses and three live-born babies), and after therapy, it was 90.5% (21 pregnancies and 19 live-born babies). Pre-term delivery due to maternal or fetal indications was required in 15% (3/20) of the viable pregnancies. Except for prematurity (20% of viable pregnancies) and its potential associated complications, there were no significant adverse effects to either mothers or babies. Our treatment modality is advocated for prevention of pregnancy losses in patients with the 'obstetric' primary antiphospholipid syndrome.