Plasma antithrombin III levels in pre-eclampsia and chronic hypertension.

Plasma levels of antithrombin III were tested during pregnancy in a control group of normal patients and in a study group that included patients with moderate and severe pre-eclampsia and chronic hypertension. The control group showed mean antithrombin III activity of 97.9 +/- 20.9%, the severe pre-eclamptic patients 22.33 +/- 18.22%, the moderate pre-eclamptic patients 56.0 +/- 7.56%, and the chronic hypertensive patients 77.5 +/- 6.69%. The difference between normal pregnancy and moderate pre-eclampsia was significant at P less than 0.002, normal pregnancy and severe pre-eclampsia P less than 0.002, moderate and severe pre-eclampsia P less than 0.002, chronic hypertension and normal pregnancy P less than 0.1, and chronic hypertension and severe pre-eclampsia P less than 0.002. All the severe pre-eclamptic patients and 2 out of 6 of the moderate pre-eclamptic women were below 55.7% (mean - 2S.D.) of normal antithrombin III activity. Patients with heavy proteinuria had depressed antithrombin III activity. However, chronic hypertensive pregnancies, although rather a small group, had almost normal values of plasma antithrombin III activity. The plasma antithrombin III value may thus help to distinguish between chronic hypertension and severe pre-eclamptic disease.