We evaluated the known metabolic effects of aspirin in pregnant hypertensive patients. Eighty-seven pregnant women (12th-24th gestational week) were randomly allocated to low-dose aspirin or placebo treatment. Between the 24th-28th gestational week the following tests were performed: oral glucose tolerance test, venous blood pH and base excess, coagulation profile, platelet count, morning (8 a.m.) cortisol, creatinine clearance and serum uric acid. A significantly higher serum uric acid level was detected in the low-dose aspirin group (5.6±2.2 mg/dl) compared with the placebo group (4.7±1.2 mg/dl, p=0.048). No other significant difference was found for any of the other parameters tested. We conclude that low-dose aspirin treatment during the second half of pregnancy in hypertensive patients seems safe in terms of its effect on various maternal metabolic effects.