RED CELL SIZE AND FETAL HEMOGLOBIN CONCENTRATION IN THE NEWBORN INFANT

Abstract

At birth, the newborn infant has a heterogenous population of erythrocytes; variability exists with respect to size, shape, enzymatic capacity and hemoglobin composition. Employing both differential staining for fetal hemoglobin and cytophotometric techniques, the erythrocytes of term infants were examined in an attempt to relate cell size to hemoglobin composition. One-hundred and twenty cells from each infant were individually sized and subjected to micro-densitometry measurements. Sixty of the cells had been eluted and counter-stained for fetal hemoglobin. The staining for fetal hemoglobin did not alter the size of the cells. Analysis revealed that as the red cells increased in size the concentration of fetal hemoglobin within the cells decreased significantly more than did the total hemoglobin concentration. Cells with a diameter of approximately 6 μ had almost exclusively fetal hemoglobin. These findings are consistent with the hypothesis that the largest, and presumably the youngest, erythrocytes are synthesizing less fetal hemoglobin at the time of birth than cells that had been produced some weeks before. The use of cytophotometry provides a technique for following cohorts of cells with varying ages and hemoglobin composition.

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