Is maternal whole blood viscosity a factor in fetal growth?

Many authors have correlated changes in maternal hemodynamics during pregnancy with fetal growth. Sufficient plasma volume expansion in pregnancy seems mandatory for an optimal reproductive result. A correlation between rheological characteristics (low-shear whole blood viscosity and yield shear stress) and birthweight centiles was found in 26 third-trimester pregnancies. The level of statistical significance (P less than 0.05) was reached in nulliparous pregnancies but not in parous pregnancies. Measurements of whole blood viscosity at low shear rate and yield shear stress seem to provide information on the efficacy of placental perfusion. There have been reports in the literature to support the assumption of the prevalence of low-shear circumstances in the intervillous space. The hypothesis is put forward that, during pregnancy, the changes in maternal hemodynamics influence fetal growth by their impact on the flow through the placenta.