The effect of pregnancy on the activity of SLE and that of SLE on the product of conception was analyzed from data reported in nine series of 20 or more pregnancies published between 1956 and 1981. Although pregnancy has an adverse effect on SLE activity, an established diagnosis of SLE does not preclude an outlook for a successful pregnancy even in patients with previous signs of severe multisystem involvement and lupus nephropathy. Complete clinical remission for 6 mo or more prior to conception indicates a favorable prognosis for an uncomplicated course during pregnancy and a live birth. Continued signs of disease activity or renal disease reduce, however, the likelihood for an uncomplicated course and decreases the live birth rate by 25% - 30%. Since there is no evidence that glycocorticoids or cytotoxic agents affect fetal development or induce congenital abnormalities treatment during pregnancy should be directed towards suppression of disease activity and controlling hypertension.