Heparin cofactor activity and antithrombin III antigen levels in preeclampsia.

It has been reported that patients with preeclampsia have decreased levels of antithrombin III heparin cofactor and that the degree of depression parallels the severity of disease. To determine the time course of development and resolution of this deficiency, and to gain insight into the cause of this deficiency, plasma antithrombin III antigen and heparin cofactor activity levels were measured serially in 11 women with mild preeclampsia. Although the ATIII antigen level remained stable during the antepartum period, the level of heparin cofactor was noted to fall progressively during the antepartum period. Both ATIII antigen and heparin cofactor increased promptly postpartum. The discrepancy between the levels of ATIII antigen and heparin cofactor activity suggests that in both mild and severe preeclampsia there is utilization of antithrombin III to form inactive protease inhibitor complexes.