Activation contact system (ACS) and tissue factor (TF) in human amniotic fluid: Measurements of ACS components and TF, and some implications on the pathophysiology of amniotic fluid embolism

Abstract Background/Aim It is believed that the amniotic fluid-derived TF, in the case of amniotic fluid embolism(AFE), contributes to acute disseminated intravascular coagulation (DIC) and obstetric shock in the mother. However, the role of amniotic fluid-derived contact phase coagulation factors that irrupt into the bloodstream simultaneously with TF is still unknown. Our study objective was to identify and measure the concentrations of CAS components and TF in amniotic fluid. Material and methods The study group consisted of 30 healthy parturients with uneventful pregnancy and birth. Amniotic fluid (AF) and maternal blood were sampled at the end of the first stage of labor. The components of ACS, i.e. factors XII and XI (FXII, FXI), prekallikrein (PK), high molecular weight kininogen (HMWK), and tissue factor (TF) were measured by immunoenzymatic method (ELISA). Results All ACS components were detected in AF; their levels were higher in AF than in the maternal plasma: FXII - 29.17 ng/mg protein vs. 0.94 ng/mg protein (medians); FXI - 27.28 ng/mg protein vs. 0.92 ng/mg protein (medians); PK - 88442.04 ng/mg protein vs. 113.44 ng/mg protein (medians); HMWK - 4253.82 ng/mg protein vs. 2857.96 ng/mg protein (medians). The concentration of TF in amniotic fluid was 39.46 pg/mg protein (median) vs. 0.41 pg/mg protein (median) in blood plasma. Conclusions 1.The ACS components, i.e. FXII, FXI, PK and HMWK, are the constituents of amniotic fluid. 2.The concentrations of the amniotic fluid-derived factors having a coagulation initiation potential, i.e. TF and contact phase coagulation factors, are higher in amniotic fluid than in mother’s blood plasma.