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

Abstract

The levels of haemostatic variables in amniotic fluids of normal 2nd trimester of pregnancy and during labour were determined. t-PA antigen and PAI-1 levels were significantly increased during labour in comparison to 2nd trimester. t-PA/inhibitor complexes and single-chain urokinase plasminogen activator (scu-PA) were present with free t-PA seen only during labour but not during 2nd trimester pregnancy. PAI-1 activity was not detectable during 2nd trimester but a mean value of 23.2 ± 14 AU/ml was observed during the labour. PAI-2 antigen levels remained elevated whilst fibrinogen, Factor X and plasminogen were not detectable in the amniotic fluids studied. Functional ATIII was not detected during labour but low activity (mean 21.3 ± 8.9%) was seen in 21 of the 25 amniotic fluid samples collected in 2nd trimester of pregnancy. ATIII antigen levels of mean 0.015 ± 0.005 g/L and 0.012 ± 0.003 g/L were found during the 2nd trimester and labour respectively. Significant increase in t-PA activity in maternal plasma as compared to amniotic fluid was observed during labour although no significant differences in u-PA, PAI-2 and PAI-1 activity levels were observed. The increased fibrinolytic activity in the plasma during labour and an overwhelming inhibitory capacity of the amniotic fluid prepare the subject for the haemostatic challenge of delivery.