The relation of red cell size to fetal hemoglobin concentration in the term infant

The relation of red cell size to fetal hemoglobin concentration was examined in blood smears prepared from term infants. Cells were examined by microdensitometry before and after elution of adult hemoglobin. The elution process did not alter cell size. Analysis reveals that the small erythrocytes contain significantly greater proportions of fetal hemoglobin than do the larger erythrocytes and is consistent with the observations that the youngest, and largest, erythrocytes are synthesizing less fetal hemoglobin at the time of birth.