Fibrinolytic Activity of Veins During Pregnancy

The fibrinolytic activity of the blood progressively decreases during pregnancy, and in the last month it is often barely demonstrable—not even after venous stasis. The fibrinolytic activity in the venous walls, as determined histochemically in venous biopsy specimens, is significantly reduced throughout pregnancy. It appears that the change in hormone balance during pregnancy results in a reduction of the synthesis of activators in the vessel walls and/or inhibition of the release of such activators to the blood stream.