Coagulation activation markers do not correlate with the clinical risk of thrombosis in pregnant women

Objective: Because coagulation activation markers have been shown to indicate an increased risk of thrombosis, we tested whether thrombin–antithrombin III complexes and D -dimers correlated with the risk assessment in pregnant women on the basis of clinical data. Study Design: We divided a group of 261 pregnant women (305 pregnancies) into low- and high-risk groups according to the personal and family histories of thrombosis and the presence of a hereditary or an acquired thrombophilia. Women with a thrombotic event in the current pregnancy formed a separate group. All pregnancies with or without heparin therapy were closely monitored with thrombin–antithrombin III and D -dimer values for the entire course of the pregnancy. Retrospectively, the data were then correlated with the different groups and subgroups. Results: The course of the mean thrombin–antithrombin III values of all 305 pregnancies was close to or slightly above the upper cutoff line, whereas the D -dimer values were well within the normal range. Independent of heparin, there was no difference in the course of the thrombin–antithrombin III and D -dimer values between the low- and high-risk groups. Only women with ongoing thrombosis during pregnancy had significantly higher thrombin–antithrombin III and D -dimer values with or without heparin therapy. Among those individuals with elevated thrombin–antithrombin III or D -dimer values, there were no specific, recognizable patients who had elevated markers more often than others. Conclusions: Thrombin–antithrombin III and D -dimer values do not correlate with a risk stratification assessed by clinical criteria. There are many women at low clinical risk who have elevated markers, and there are many women at very high clinical risk who have normal markers. Thus thromboprophylaxis would often be used inadequately if the indication were based on coagulation markers. (Am J Obstet Gynecol 2001;184:382-9.)