Amniotic fluid plasminogen activators and inhibitors and TAT-complex levels during 2nd trimester pregnancy and labour

Activation of coagulation in amniotic fluid during normal human pregnancy

INTRODUCTION

Amniotic fluid (AF) is an important medium for fetal development which exhibits high procoagulant activities; however, the role of these procoagulants during pregnancy has not been elucidated and might be associated with pregnancy complications. The current study aimed to evaluate factor X (FX) activation and its association with tissue factor (TF), tissue factor pathway inhibitor (TFPI) and coagulation activation markers in AF during normal human pregnancy.

METHODS

Activation of FX and concentration of TF, free TFPI, D-dimer and prothrombin fragments (F1+2) were evaluated in AF samples obtained for chromosome analysis from 91 women with normal pregnancy: 65 samples were taken from patients at 16-20 weeks of gestation, 9 samples were drawn at 21-30 weeks and 17 samples--after 30 weeks of gestation.

RESULTS

Activation of FX in AF significantly increased during normal pregnancy (from 65±41 to 205±80 equivalent RVV ng/mg total protein, P<0.0001). TF and TFPI levels in AF also rose with gestational age. In contrast, the AF concentration of D-dimer and F1+2, markers of coagulation activation significantly decreased when expressed per mg total protein. Levels of free TFPI correlated with TF (r=0.5, P<0.001), and were 8-fold higher than those of TF during pregnancy.

CONCLUSION

High levels of TFPI might be associated with the inhibition of procoagulant activity in amniotic fluid during normal pregnancy, which may account for the rarity of clinical amniotic fluid embolism.

Effect of amniotic fluid on coagulation and platelet function in pregnancy: an evaluation using thromboelastography

Amniotic fluid embolism is a rare obstetric complication. The exact pathogenesis of this syndrome remains unknown and significant controversy exists whether coagulopathy should always be present. We used thromboelastography to assess the effect of amniotic fluid on coagulation and platelet function in pregnant women. Different volumes of amniotic fluid (10-60 microl) were added to blood (330 microl) from pregnant women and thromboelastography variables determined. There were three important findings. R time, reflecting time to first clot formation, was significantly decreased with the addition of 10 microl amniotic fluid; platelet function, as determined by Reopro-TEG technique, was increased with the addition of 30 microl of amniotic fluid; and there was no evidence of fibrinolysis in any samples studied. In conclusion, our study substantiates the hypothesis that coagulation profile changes are invariable accompaniments of amniotic fluid embolism.

Plasminogen, alpha(2)-antiplasmin and complexes of plasmin-alpha(2)-antiplasmin (PAP) in amniotic fluid and blood plasma of parturient women

The aim of the present study was to determine whether the following components of the fibrinolytic system are present in amniotic fluid: plasminogen, plasmin and alpha(2)-antiplasmin, and plasmin-alpha(2)-antiplasmin (PAP) complexes. The study group consisted of 30 healthy women giving birth at term; 10 nonpregnant women constituted a control group. Plasminogen and alpha(2)-antiplasmin were studied by using an amidolytic method, and PAP by an ELISA method. The levels of plasminogen and alpha(2)-antiplasmin in amniotic fluid are low, 1.57+/-0.82 and 6.80+/-3.09%, respectively, of the values in blood plasma. The PAP concentration in amniotic fluid (70.61+/-14.28 microg/l) was also lower than in blood plasma (247.19+/-111.39 microg/l). We concluded that in amniotic fluid plasminogen and alpha(2)-antiplasmin are present, but at a concentration lower than in plasma. The presence of PAP in amniotic fluid is an evidence of two processes in the amniotic cavity: (i) plasmin generation, and (ii) plasmin inactivation by alpha(2)-antiplasmin.

An assessment of the effects on coagulation of midtrimester and final-trimester amniotic fluid on whole blood by Thrombelastograph analysis

The Thrombelastograph((R)) test (TEG; Haemoscope Corporation, Skokie, IL) was used to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Different volumes of midtrimester and final-trimester AF were added to whole blood from nonpregnant volunteers in a series of TEG tests. The addition of both midtrimester and final-trimester AF resulted in significant decreases in reaction time (P < 0.001) and time from reaction to a fixed level of clot firmness (P < 0.05) and significant increases in angle (P < 0.05) and coagulation index (P < 0.05) values. This reflects accelerated clot initiation and propagation. There was no significant change in the maximal amplitude or % lysis at 30 and 60 min with the addition of either midtrimester or final-trimester AF. There was no significant difference between the effects of midtrimester and final-trimester AF on whole blood TEG. TEG may be an additional useful tool in the treatment of coagulopathy in AF embolism.

IMPLICATIONS

We used the Thrombelastograph((R)) test (Haemoscope Corporation, Skokie, IL) to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Results demonstrate that AF accelerates clot initiation and propagation. The Thrombelastograph((R)) test may be useful in assessing coagulopathy in patients with AF embolism.