Minor fetal hemoglobins in relation to gestational age

Cord blood samples were obtained at delivery in 44 normal women, at gestational periods ranging from 27 to 41 weeks. All women had a normal glucose screening test and 15 were delivered preterm. With the use of Biorex 70 chromatography, red cell lysates were analyzed to determine the percentages of the different hemoglobin (Hb) components, i.e., HbF1a+b, HbFlc, HbFo, and HbA. The percentage of HbFla+b in fetal blood was higher than the corresponding percentage in adult blood. The percentages and ratios of the various Hb components were compared in preterm and term fetuses and their correlation to gestational age was tested. HbF and HbF/A ratios were higher in preterm fetuses and were negatively correlated with gestational age. HbA and HbA/F ratios were lower in preterm fetuses than in term fetuses and correlated positively with gestational age. The percentages of minor components HbFla+b, and HbFlc were not significantly different in the preterm and the term fetuses, and they did not have statistically significant correlation with gestational age. However, the ratios of these minor hemoglobins to HbF, i.e., HbFla+b/HbF, and HbFlc/HbF and HbFl/HbF were found to be significantly higher in term fetuses as compared to preterm fetuses and to correlate positively with gestational age. This is probably due to the gradual lengthening of the life span of fetal erythrocytes as term approaches, which results in the erythrocytes' increased exposure to the glycolytic intermediates and possibly to glucose.