QUANTITATION OF THE THROMBOTIC EFFECTS IN ARTERY AND VEIN OF THE INCREASE IN COAGULATION FACTORS DURING NORMAL PREGNANCY IN THE RAT

Abstract

Coagulation factors increase and fibrinolysin activity decreases in pregnant women. While the nett change in thrombotic tendency is unmeasured, venous thromboembolism increases five-fold in this group. We measured thrombus formation in vein and artery on standard platinum wires in 45 near-term pregnant rats, 19 pregnant for the first time and 26 for the second time, and in 33 never-pregnant controls. No significant increase in arterial thrombus occurred in the pregnant rats. Venous thrombus, however, increased by 65% in rats pregnant for the first time and 176% in those pregnant for the second time, compared to never-pregnant animals. Their mean increase in coagulation factors VIII, X, V, VII and II varied from 165 to 268%. Factor VIII level (r=0.59, p<0.05) correlated with venous thrombosis level, but the rarity of spontaneous thrombosis did not permit the limits of risk to be determined. Factors VII, X and V showed little correlation with thrombus weight (r=<0.16) and Factor II an insignificant one. Monitoring factor VIII levels in pregnant women might help identify a group at risk of thromboembolism and establish a threshold for prophylactic intervention. © 1997 Elsevier Science Ltd