Plasma antithrombin III activity: an aid in the diagnosis of preeclampsia-eclampsia.

Plasma antithrombin III (AT III) activity was examined retrospectively in patients with preeclampsia-eclampsia, chronic hypertension, and chronic hypertension with superimposed preeclampsia-eclampsia. Levels of AT III were greater than 1 SD below normal pregnant control in each case of preeclampsia-eclampsia syndrome. The degree of reduction in plasma AT III activity was correlated with the severity of disease. AT III activity was within normal limits in patients with chronic hypertension. AT III activity dropped prior to the appearance of clinically evident disease in three patients who were followed from an early gestational age. In no instance was low plasma AT III activity associated with normal pregnancy. Coincidental disease, including pyelonephritis and a viral syndrome, were associated with markedly decreased levels of plasma AT III activity in otherwise normal pregnancies. Plasma AT III activity may be valuable as a tool in diagnosing preeclampsia-eclampsia, as a screening test for preclinical preeclampsia-eclampsia, and as an indicator of severity of disease.