The Effect of Iron Supplements and Blood Transfusion on Iron Absorption by Low Birthweight Infants Fed Pasteurized Human Breast Milk

摘要

Summary: Using serial metabolic balances, iron absorption was measured in six preterm infants (mean gestational age 29 weeks), and two fullterm small for gestational age (SGA) infants, between day 10 and 70 after birth. They were all fed breast milk. Iron supplements (2.5–13 mg/kg day) were given from day 30. Three preterm infants received blood transfusions for anemia. During the first 30 days of life iron balance was negative in the preterm infants (mean ± SEM = ?0.10 ± 0.02 mg/kg day) and positive in the full term SGA infants (mean ± SEM = 0.098 ± 0.02 mg/kg day). In infants who were not transfused, absorption of supplementary iron was a linear function of iron intake, and corresponded closely to 34% absorption. An iron intake of 5–6 mg/kg day resulted in the absorption of amounts of iron close to those being laid down in utero. Blood transfusion was followed by a reduction in iron absorption; in two cases it became negative, becoming positive again as the hemoglobin fell below about 12.0 g/100 ml. These data show that a mechanism exists in preterm infants for the control of iron absorption which does not operate at the hemoglobin concentrations that prevail in such infants, unless they are transfused.Speculation: The data suggest that in preterm infants there is a lack of correspondence between the amount of iron absorbed on the one hand, and hemoglobin synthesis and concentration in the blood on the other. We speculate that if preterm infants maintained their hemoglobin concentration at 11–12 g/100 ml as do full term infants, iron absorption might come under feedback control rather than being a function of the concentration in the diet.