Erythrocyte indices in the second trimester of pregnancy: are reference values well established?

Abstract

The erythrocyte index values in the pregnancy-puerperal cycle behave in a particular manner, however, the physiological or nosological meaning of such alterations are not well established. This study was aimed at analyzing the distribution of erythrocyte indices in the second trimester of pregnancy. The study was carried out with secondary data from 347 pregnant women in the 2nd trimester of low-risk prenatal care at the Instituto Materno Infantil Professor Fernando Figueira (Recife, Brazil) between May 2000 and June 2001. Measurements were performed using an automatic counter. Frequency distribution curves of erythrocyte indices (means and standard deviations) and correlation curves of hematocrit (HTC) and hemoglobin (Hb) concentrations were constructed. The mean red blood cell number (RBC) was 3.7 x 10(12)cells/L; mean HTC was 32.9% and mean Hb was 10.8 g/dL; the values exhibited Gaussian distributions. The mean morphological values were 88.4 fL for the mean corpuscular volume; 29.0 pg for the mean corpuscular hemoglobin and 32.8 g/dL for the mean corpuscular hemoglobin concentration; these values were not adjusted to Normal distributions. HTC values were three times higher than Hb values. Mean RBC, HTC and Hb values (used in the diagnosis of anemia) were lower than thresholds considered normal and exhibited Gaussian distributions. Morphological indices remained within normal ranges, but without delineating a Normal curve. As expected HTC and Hb values behaved following a linear correlation.