Tissue factor and its natural inhibitor in pre-eclampsia and SGA

Tissue factor (TF), the major activator of the extrinsic pathway of coagulation, is abundant in the placenta and decidua. The aim of this study was to determine the maternal plasma concentrations of TF and its primary inhibitor, tissue factor pathway inhibitor (TFPI), in women who delivered small for gestational age (SGA) neonates, and in pre-eclampsia.

A cross-sectional study included the following groups: 1) women with normal pregnancies (n = 86); 2) patients who delivered SGA neonates (n = 61) and 3) women with pre-eclampsia (n = 133). Maternal plasma concentrations of TF and TFPI were measured by a sensitive immunoassay. Non-parametric statistics were used for analysis.

1) Women with pre-eclampsia had a significantly higher median plasma concentration of TF than patients with a normal pregnancy (median: 1187 pg/mL; range: 69-11675 vs. median: 291.5 pg/mL; range: 6.3-2662.2; p < 0.0001, respectively); 2) Similarly, TFPI concentrations were higher in pre-eclampsia than in normal pregnancy (median: 87.5 ng/mL; range 25.4-165.1 vs. median: 66.1 ng/mL; range: 14.3-86.5; p < 0.0001, respectively); 3) Surprisingly, mothers with SGA neonates had a lower median maternal plasma concentration of TF (median: 112.2 pg/mL; range: 25.6-1225.3) than women with a normal pregnancy (p < 0.0001).

1) Maternal plasma concentrations of TF in patients with pre-eclampsia, but not in those who delivered an SGA neonate, were higher than in women with normal pregnancies; 2) Although the role of immunoreactive plasma TF in coagulation remains controversial, our observations suggest that changes are present in the context of complications of pregnancy.