Thrombin-inhibitor complexes in the blood during and after delivery.

Activation of coagulation leads to generation of thrombin which in turn is inactivated by the formation of thrombin-antithrombin (TAT) complexes, and thrombin-heparin cofactor complexes (T-HCII). These complexes were measured in plasma by ELISA methods. During normal delivery, the median TAT level in ten women increased from 4.1 to 7.8 times the median normal reference level. There was great individual variation, and levels 42 and 56 times normal median were found in two women shortly after normal delivery. The median T-HCII levels increased only moderately from 2.3 to 3.1 times median normal reference. D-dimer values were elevated in 28 out of the 30 samples. In blood sampled 1-2 days after delivery, the median TAT level was 2.5 times the median normal reference. The median T-HCII level was now 5.6 times the median normal reference value. The values were stable during the first 4 days post partum, and there was little difference between those delivered vaginally or by Caesarean section (C-section). D-dimer values were above normal reference in all women, and higher in women delivered by C-section. In conclusion, increasing TAT levels during labour and delivery indicated generation of thrombin which was mainly inactivated by antithrombin. The T-HCII levels increased less during delivery. In the early post partum period, the T-HCII levels were relatively more increased than the TAT levels. These results suggest that intravascularly generated thrombin is preferably inactivated by antithrombin, even in parturient women. In the post partum period, formation of T-HCII complexes was more evident, possibly reflecting extravascular inactivation of thrombin.