Pregnancy markedly alters a normal woman's physiology and immune response mechanisms. The effect of pregnancy changes on the course of systemic lupus erythematosus (SLE) remains, however, speculative. Pregnant lupus patients are susceptible to pre-eclampsia, especially if they suffer lupus nephritis, and to steroid-induced hypertension and hyperglycemia. Fetuses are susceptible to placental insufficiency if antiphospholipid antibody or other procoagulant states are present, and to neonatal lupus if anti-Ro/La antibodies are present. Artificial reproductive technologies ("in vitro fertilization") can be safely used in SLE patients. Study of the physiology of pregnancy, for instance complement kinetics, may inform our understanding of SLE, and vice versa.