Summary
Forty-eight healthy pregnant women were studied prospectively and longitudinally.
Blood sampling was performed at 10-15, 23-25, 32-34 and 38-40 weeks of gestation,
within one week and at eight weeks postpartum. Classic and modified activated protein
C ratio decreased as pregnancy progressed. In the third trimester 92% of the ratios
measured with the classic test were above the lower reference level whereas all modified
test ratios were normal. Slight activation of blood coagulation was shown with increased
levels of prothrombin fragment 1+2, soluble fibrin and D-dimer. Fibrinogen, factor
VIII and plasminogen activator inhibitor type 1 and type 2 increased. Protein S and
tissue plasminogen activator activity decreased. Protein C remained unchanged. No
correlation was found between the decrease in classic APC ratio and changes in factor
VIII, fibrinogen, protein S, prothrombin fragment 1+2 or soluble fibrin, nor between
the increase in soluble fibrin and changes in prothrombin fragment 1+2, fibrinogen
and D-dimer.