Changes in age distribution of erythrocytes during pregnancy: a longitudinal study.

This prospective study was undertaken to evaluate age distribution of erythrocytes longitudinally throughout pregnancy. Serial estimates of density distribution of cells (DDC), reticulocyte count, red cell distribution width (RDW), and mean corpuscular volume (MCV) in a group of healthy pregnant women at 12, 16, 20, 24, 28, 32 and 36 weeks gestation and during the latent phase of labor (39.04 +/- 1.5 weeks). MCV increased constantly during pregnancy; however, the increase was not statistically significant. The mean reticulocyte percentage rose significantly at the 28th week, thereafter it remained at high levels until delivery. RDW increased significantly at the 20th week, remained at high levels until the 32nd week and thereafter declined towards the delivery. The cumulative DDC curve gradually shifted to the right during pregnancy, indicating a less dense cell population as the pregnancy progressed. In conclusion, a continuous alteration in age distribution of erythrocytes towards a younger cell population takes place from early pregnancy until the delivery of the fetus.