Depletion of iron stores is the first step in the continuum of changes that occur in iron deficiency. Iron deficiency induces biochemical defects (such as impaired synthesis of DNA and collagen) even before any features of microcytic, hypochromic anemia become evident. The rapidly maturing preterm brain is especially vulnerable to the effects of iron deficiency; poor school-age performance has been reported among children who had low iron stores in their neonatal period.