Iron retention in preterm infants fed low iron intakes: a metabolic balance study.

There is little data on iron retention in healthy preterm infants. Twenty-four metabolic balance studies were carried out in 13 preterm infants between 17 and 63 days of age, in 11 cases 2 balance were carried out 7d apart. Iron intake was 1.11 mg/kg/day (SD 0.06), less than the 2 mg/kg/d typically recommended for preterm infants. Iron retention was positive in the majority (3/13) of the first balances, and in all 11 of the second balances. Iron retention increased significantly between the two balances (from 0.095 mg/kg/d (SD 0.178) to 0.270 (SD 0.209)). Iron retention was significantly related to the time that the infant had been on enteral feeds at the time the balance was carried out. Iron retention was significantly greater than the requirement estimated to be needed to meet the needs for growth and expansion of the circulating red cell mass. Iron intakes of about 1mg/kg/d seem to be adequate to support the requirements for growth in preterm infants during this time period, but are significantly less than the estimated in utero accretion rate of the fetus.