Antithrombin III levels in preeclampsia.

Antithrombin III (AT-III) activity was measured and compared in 29 patients with preeclampsia and 31 women with normal pregnancies. AT-III levels were 83 +/- 25% in preeclamptic patients with greater than 5 g/l proteinuria compared with 102 +/- 11% in the controls. Less severe proteinuria was not associated with decreased AT-III levels. Multivariate analysis revealed that the duration of pregnancy and the degree of proteinuria had an independent negative effect on AT-III levels. AT-III activity correlated poorly with platelet counts and blood pressure measurements. We conclude that urinary loss appears to be the major mechanisms of lower AT-III levels observed in our patients with preeclampsia.