Blood viscosity at a low shear rate in normal and abnormal pregnancies

Blood viscosity and corrected blood viscosity (viscosity of blood corrected to hematocrit of 45 %) were measured at a shear rate of 0.5 sec⁻¹ in 85 normal, 20 mild pre-eclamptic, 15 severe pre-eclamptic and 10 diabetic (class A) pregnants. Viscosity in normal pregnancy decreased in the second trimester and increased in the third trimester. Corrected viscosity increased in the second trimester and its increased level persisted until the last of pregnancy. The mean levels of viscosity and corrected viscosity in the third trimester did not change in mild pre-eclampsia, but were significantly increased in severe pre-eclampsia as compared with that of normal pregnancy. In diabetic pregnancy viscosity was not significantly different but corrected viscosity was significantly higher than that of normal one. These findings are in keeping with an increased tendency of forming red cell aggregates in severe pre-eclampsia and diabetic pregnancy and may suggest possible disturbance of microcirculation in low flow state under such abnormal pregnancies.