The course of 27 pregnancies in 13 patients with systemic lupus erythematosus (SLE) is presented. The overall incidence of fetal wastage was 33.3%, a figure significantly higher than that observed in the general population. Although serum C3 complement levels rise during normal pregnancy, mean C3 levels remain within the normal range. Since it is a fall in complement levels in patients with SLE which may herald the onset of symptoms and provide a guide to therapy, assay of serum C3 complement levels remains a valid monitoring device in management of these patients during pregnancy. Flares of SLE during pregnancy generally should be treated vigorously with corticosteroids rather than by therapeutic abortion. Continuation of corticosteroid treatment during the first 2 months postpartum is advised to limit the incidence of exacerbation of SLE activity following delivery.