Early Iron Supplementation in Very Preterm Infants Fed Donor Breast Milk: A Prospective, Interventional, Clinical Trial

In preterm and low birth weight (LBW) infants, moderate-certainty evidence indicates that feeding with commercial infant formula compared with donor breast milk (DBM), either as a supplement to maternal expressed breast milk (MBM) or as a sole diet, results in higher rates of weight gain, linear growth, and head growth but is associated with a higher risk of developing necrotizing enterocolitis (NEC)1-5. Despite the decreased incidence of NEC, DBM has been shown to be inferior to MBM in terms of overall growth. This is attributed to the fact that DBM contains significantly less protein, fat and energy than the milk provided by the mothers of preterm infants. Hence, it is considered standard of care to supplement MBM and DBM with commercial fortifiers.

Yet, considering the extraordinarily high morbidity and mortality, along with the significant economic burden, associated with NEC, the current standard of care is to provide DBM, initially unfortified and subsequently fortified, in lieu of formula in cases where MBM is unavailable or contraindicated. Such DBM, provided by local milk banks are pasteurized prior to shipment, according to standard protocols. Evidence exists for significantly lower iron content in post-pasteurized DBM as compared to pre-pasteurized DBM.

Results from a prospective observation clinical study in 2024 at Advent Health for Children in 34 very preterm infants randomized to receive either DBM or MBM and adjusted for duration of cord clamping, fortification progression and iron supplementation practice, demonstrate that very preterm infants fed DBM have a significantly lower ferritin level at 2 weeks (178.47 vs. 230.06 ng/ml, p=0.04) and hematocrit at 4 weeks (27.41 vs. 32.05%, p= 0.03) (Pulickal et. al. PAS 2025) These reduced levels of serum ferritin and hematocrit levels in DBM fed infants would be important as evidence suggests that iron levels have a correlation with neurodevelopmental outcome. A post-hoc analysis of 692 infants enrolled in the PENUT study of the NRN of the NICHD demonstrated a positive association between iron dose at 60 days and cognitive outcomes at 2 years 9. Similarly, data from a single center tertiary center showed that delayed cord clamping in term infants was associated with higher ferritin levels and greater brain myelination at 4 months of age 10. This was further supported in a study of 540 preterm and term infants in Nepal that showed delayed cord clamping increased ferritin levels and decreased the incidence of anemia at 8 months and 12 months 11.

An opportunity exists for appropriate clinical intervention with earlier iron supplementation based on the results of our study. Optimizing the timing of iron supplementation in DBM fed infants could attenuate the differences in hematological parameters and possibly contribute to improved neuro-developmental outcome by avoiding iron deficiency at a critical stage of infants' neurodevelopment.

The investigational component of this research is: Iron supplementation ( Ferrous sulfate, 2-4 mg/kg/day depending on the infant's body weight) will be implemented early ( approximately 4-6 days of life) when the infant achieves 80ml/kg/day of enteral feeds, as contrasted to the current protocol of full feeds (140 to 160ml/kg/day), the latter usually by Day 14 of life. At DOL 14 (± 4 days), a blood sample (0.5 mL) will be obtained for serum ferritin and hematocrit determination. Similarly, a second blood draw would be performed at DOL 28 (± 4 days) or prior to discharge, whichever comes earlier, for serum ferritin and hematocrit determination. These samples will be obtained from routine clinical blood draws thus minimizing pain and discomfort. The hematocrit may be part of standard clinical care involving routine weekly monitoring.