Developmental changes in red blood cell counts and indices of infants after exclusion of iron deficiency by laboratory criteria and continuous iron supplementation.

The developmental changes in red blood cell counts and indices were determined in infants after mild iron deficiency was excluded. The normal values were obtained from a selected group of healthy, term infants who were receiving continuous iron supplementation during a period of one year while normal values for transferrin saturation and serum ferritin were being maintained. The data indicated marked developmental changes in red blood cell counts and indices during the first year of life that are independent of iron intake. Serial analysis of individual infant's values indicated that the red cell measurement at 4 months of age are, to some extent, predictive of the level of subsequent values within the normal range.