Evaluation and modification of whole blood filtration in the measurement of erythrocyte deformability in pregnancy and the newborn.

This study was designed to investigate the deformability of erythrocytes from pregnant women and full-term newborn infants, with healthy female adults as a comparison, using a whole blood filtration method. Delay in measurement, white cells, haematocrit, plasma viscosity, temperature and pH all significantly affected the rate of whole blood filtration and could thereby obscure or exaggerate changes in erythrocyte deformability. A new method was developed which eliminated or minimized these sources of error and the study was completed. Fetal erythrocytes were found to be significantly less deformable than adult erythrocytes which were in turn found to be significantly less deformable than erythrocytes from pregnant women. These differences appear to be related to the varying plasma fibrinogen concentrations in the three groups of subjects. The significance of these findings in the special haemodynamic situations found in the neonate and during pregnancy are discussed.