Tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in amniotic fluid and blood plasma: implications for the mechanism of amniotic fluid embolism.

Tissue factor (TF) is known to be present in a high concentration in amniotic fluid. The main question of this study is whether tissue factor pathway inhibitor (TFPI), a natural inhibitor of TF, is present in amniotic fluid. The study group consisted of 28 women with normal pregnancy course, and at the first stage of termed labour. Fifteen non-pregnant women were the control group. TF and TFPI were studied by an immunoenzymatic method (ELISA). The level of TFPI in amniotic fluid was 38.7% of that in blood plasma (16.81+/-5.34ng/ml versus 43.41+/-18.70ng/ml, P<0.001), while the level of TF in amniotic fluid was 44.8 times higher than in blood plasma (9995.93+/-8533.11pg/ml versus 252.66+/-28.84pg/ml, P<0.001).

Conclusions: (i) It was found, for the first time, that amniotic fluid contains TFPI (ii) It is reasonable to assume that the intrusion of amniotic fluid into the blood-stream may influence the plasmatic TFPI-TF equilibrium resulting in intravascular blood coagulation.