Effect of low-dose aspirin during pregnancy on fibrinolytic variables before and after parturition.

OBJECTIVE We assessed the effects of a daily oral dose of 60 to 80 mg of aspirin from 12 weeks' gestation until delivery on fibrinolytic variables before and after parturition. STUDY DESIGN In a prospective controlled study labor was electively induced in 24 patients, eight receiving low-dose aspirin and 16 controls. Levels were determined in maternal and cord plasma of tissue-type plasminogen activator antigen and activity, plasminogen activator inhibitor-1 antigen, plasminogen activator inhibitor activity, and plasminogen activator inhibitor-2 antigen. We also determined metabolites of vascular prostacyclin and platelet thromboxane A2. RESULTS The only maternal fibrinolytic variable affected by low-dose aspirin was plasminogen activator inhibitor activity, which showed a significant reduction before and after parturition of 40% and 70%, respectively, in low-dose aspirin users compared with controls. Concentrations of thromboxane B2 in women using low-dose aspirin were 7% (maternal serum) and 17% (cord serum) of values in controls, but concentrations of 6-keto-prostaglandin F1 alpha were not affected. CONCLUSIONS Low-dose aspirin reduces plasminogen activator inhibitor activity and platelet reactivity, but not prostacyclin synthesis, before and after parturition. The reduction in plasminogen activator inhibitor activity may be caused by inhibition of platelet reactivity.