A longitudinal study of resting peripheral blood flow in normal pregnancy and pregnancies complicated by chronic hypertension and pre-eclampsia.

OBJECTIVES To investigate the hypothesis that reduced resting tissue blood flow precedes the clinical onset of pre-eclampsia in women at risk of the disease. METHODS We used venous occlusion plethysmography to compare resting calf muscle blood flow in 18 normal pregnant controls, 18 pregnant women with chronic hypertension, and 23 pregnant women at increased risk of developing pre-eclampsia. Calf blood flow was measured at 16, 20, 24, 28, 32 and 36 weeks of gestation. RESULTS Blood flow increased with gestation in normal pregnancy (P = 0.004) and chronic hypertension (P = 0.006), but not in the 'at risk' women who did not develop pre-eclampsia (P = 0.36). In contrast, blood flow decreased significantly in eight out of the 23 women 'at risk', who developed pre-eclampsia (P < 0.00001, ANOVA). The decrease in flow preceded the clinical diagnosis of the pre-eclampsia by several weeks. Moreover, a significant inverse correlation was observed between resting blood flow and plasma uric acid concentrations (r = -0.86, P = 0.03) in the women that developed pre-eclampsia. CONCLUSIONS We have shown that reduced resting blood flow precedes the clinical onset of pre-eclampsia independently of hypertension per se. These findings support the notion that impaired tissue blood flow may be involved at an early stage in the pathophysiology of the disease.