Pregnancy is associated with depressed fibrinolysis as judged from the decreased fibrinolytic response to venous occlusion. In order to elucidate if this decreased response is due to an increase in plasminogen activator inhibitors 1 and 2 (PAI-1, PAI-2), and/or to decreased release of tissue-type plasminogen activator (t-PA) antigen during venous occlusion, 36 women (18 women with normal pregnancy and 18 with gestational hypertension without proteinuria) were followed during pregnancy and puerperium. In each women a 20 min venous occlusion was performed in the second and in the third trimester of pregnancy and 3 days after delivery. The increase in t-PA antigen after venous occlusion relative to basal value was in the second trimester of pregnancy on average 3.7 fold, in the third trimester 4.4 fold, and so not reduced compared to non-pregnant women (3.7 fold increase). After delivery the increase in t-PA antigen was significantly enhanced (8.5 fold, p < 0.005). The fibrinolytic response to venous occlusion measured by euglobulin and t-PA activity was significantly decreased in the third trimester compared to non-pregnant values (both p < 0.005) and returned to somewhat higher (euglobulin clot lysis) or significantly higher (t-PA activity, p < 0.01) values 3 days after delivery. Decreased euglobulin and t-PA activity after venous occlusion in the third trimester coincided with significant increases in basal PAI activity, PAI-1 antigen and PAI-2 antigen (2.9, 2.5 and > 30 fold increase relative to non-pregnant values, respectively, all p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)