18 - Iron

Summary

Overview

Iron is a ubiquitous element required by virtually all cells for normal growth and metabolism. Rapidly growing and differentiating cells have particularly high iron requirements. Since preterm and term human infants have high growth rates (on a per-weight basis), it is not surprising that these infants also have high iron needs. Term infants typically acquire adequate iron stores during the last trimester of gestation, but preterm infants are relatively compromised in this respect. This fact, combined with their higher postnatal growth rates in the first year, renders preterm infants at higher risk than their term counterparts for iron deficiency and iron-deficiency anemia. This increased risk could theoretically be avoided by administering large doses of iron to the preterm infant, were it not for the concern of iron toxicity; iron plays an important catalytic role in the Fenton reaction, which creates radical oxygen species that peroxidate the lipids in cell membranes. The concern is relevant particularly in the premature infant whose plasma total iron-binding capacity (TIBC) is low and whose antioxidant defense system is immature. Thus, iron can be considered a highly necessary element with a narrow therapeutic window where both deficiency and overload contribute to significant morbidity.

Iron balance in the fetus and neonate

Iron is classically seen as an integral part of the hemoglobin molecule, and iron deficiency is thus frequently assumed to be synonymous with anemia.