THE RELATIVE RATES OF SYNTHESIS OF HEMOGLOBINS A AND F IN IMMATURE RED CELLS OF NEWBORN INFANTS

Studies were carried out to explore whether the proportion of adult and fetal hemoglobin synthesized by immature red cells of cord blood would provide a precise correlation with the degree of maturity of the newborn infant. Cord blood samples were obtained from newborn infants ranging from 25 to 43 weeks' gestation in whom the gestational age estimates from menstrual history and physical examination, including neurological examination, were in close agreement. The blood samples were incubated in an amino acid mixture containing Cl4 leucine, followed by column chromatography on DEAE Sephadex for separation of adult and fetal hemoglobin fractions. The radioactivity in the adult and fetal hemoglobin fractions was measured. The percent of radioactive fetal hemoglobin synthesized by immature red cells provided a more precise correlation with the infant's gestational age than the percent of fetal hemoglobin present in cord blood at the time of birth. The percent of radioactive fetal hemoglobin was unaffected in infants with severe erythroblastosis who had in utero transfusions. In infants with intra-uterine growth retardation, the proportion of fetal hemoglobin being synthesized was significantly greater than expected for the estimated gestational age.