Background/Aim: Serum transferrin receptor(STfR), a marker of iron status and erythropoiesis, correlates directly with erythropoietic activity and inversely with the amount of iron. In newborns, cord sTfR may or may not be influenced by maturity: positive correlations or no relation between sTfR and gestation have been reported. Male term neonates have been reported to have higher or similar sTfR than female term newborns. We purport to determine whether cord serum sTfR and iron indices are influenced by maturity or by gender. We hypothesized that preterm newborns would have lower sTfR than term newborns, possibly related to limited fetal iron supply, and gender difference in fetal erythropoiesis is present in preterms.
Methods: Cord serum sTfR, iron, and ferritin concentrations were analyzed in 37 preterm and 60 term newborns (gestation 32.3¡3/4 1.1 vs 39.2¡3/4 0.3wks; birth weight 2.09¡3/4 1.1 vs 3.3¡3/4 0.4kg). In preterm, 17 were males, and 20 females; in term, 28 males and 32 females. Results: In preterm vs term newborns, cord serum sTfR was similar(33.2¡3/4 14.2 vs 28.7¡3/4 1.5ng/ml, p=0.23), cord serum iron was significantly lower (95.4¡3/4 62.5 vs 175¡3/4 59.3 g/dL, p<0.001), cord serum ferritin was higher (194.6¡3/4 130.5 vs 155.7¡3/4 95.1 g/dL, p<0.01), and reticulocytes were higher (4.4¡3/4 1.7 vs 2.8¡3/4 1.5%, p<0.01), whereas hemoglobin was not different between groups (15.7¡3/4 1.4 vs 15¡3/4 1.2, p=0.07). Cord serum sTfR was not different by gender, either in preterm or term infants. Cord serum iron correlated positively with gestation (r=0.396, p<0.01). Cord serum sTfR correlated positively with cord hemoglobin (r=0.414, p<0.001), but not with cord iron, ferritin or reticulocytes.
Conclusions: Thus, cord serum sTfR was not influenced by maturity or by gender; and indices of iron status were influenced by maturity, but not by gender. Since sTfR reflects fetal erythropoietic activity, we speculate that fetal erythropoiesis in preterm newborns may be maintained despite relative limited iron availability.