Association of antithrombin activity with plasma aldosterone concentration and plasma renin activity in pregnant women.

OBJECTIVE To test the hypothesis that the blood antithrombin (AT) activity is correlated with the plasma aldosterone concentration (PAC), the plasma renin activity (PRA), and/or the PAC-to-PRA ratio during the late stage of pregnancy. METHODS The AT activity, PAC, and PRA were determined within 7 days prior to delivery in 47 women, consisting of 30 normotensive and 6 hypertensive women with singleton pregnancies and 11 normotensive women with twin pregnancies. RESULTS The median values of the 47 women were 86% of the normal activity level for the AT activity, 442 pg/mL for the PAC, 3.7 ng/mL/h for the PRA, and 108 pg/mL per ng/mL/h for the PAC-to-PRA ratio. Women with an AT activity ≤86% had a significantly lower PRA and a higher PAC-to-PRA ratio than women with an AT activity >86% (3.5 ± 3.0 vs. 6.6 ± 4.7 ng/mL/h for PRA, p = 0.008; 156 ± 109 vs. 97 ± 46 pg/mL per ng/h for PAC-to-PRA ratio, p = 0.021). The AT activity was significantly correlated positively with the PRA and negatively with the PAC-to-PRA ratio. CONCLUSIONS The existence of a common pathophysiological background between a reduced AT activity and a reduced PRA during the late stage of pregnancy was suggested.