Iron deficiency and anemia in iron-fortified formula and human milk-fed preterm infants until 6 months post-term.

PURPOSE: An iron intake of >2 mg/kg/d is recommended for preterm infants. We hypothesized that human milk (HM)-fed preterm infants require iron supplementation after discharge, whereas iron-fortified formulae (IFF; 0.8-1.0 mg iron/100 ml) may provide sufficient dietary iron until 6 months post-term.

METHODS

At term age, 3 and 6 months post-term, ferritin (μg/l) was measured in 92 IFF-fed infants (gestational age (median (interquartile range)) 30.7 (1.4) weeks, birth weight 1,375 (338) gram) and 46 HM-fed infants (gestational age 30.0 (1.7) weeks, birth weight 1,400 (571) gram). Iron intake (mg/kg/d) between term age and 6 months post-term was calculated.

RESULTS

Iron was supplemented to 71.7% of HM-fed and 83.7% of IFF-fed infants between term age and 3 months post-term and to 13% of HM-fed and 0% of IFF-fed infants between 3 and 6 months post-term. IFF-fed infants had an iron intake from supplements and formula of 2.66 (1.22) mg/kg/d between term age and 3 months post-term and 1.19 (0.32) mg/kg/d between 3 and 6 months post-term. At 3 and 6 months post-term, the incidence of ferritin <12 μg/l was higher in HM-fed compared to IFF-fed infants (23.8 vs. 7.8% and 26.3 vs. 9.5%, P < 0.02).

CONCLUSION

This observational study demonstrates that ferritin <12 μg/l is more prevalent in HM-fed infants until 6 months post-term. This may be due to early cessation of additional iron supplementation. We speculate that additional iron supplementation is not necessary in preterm infants fed IFF (0.8-1.0 mg iron/100 ml), as they achieve ferritin ≥12 μg/l without additional iron supplements between 3 and 6 months post-term.