Comparison of two commercially available liquid human milk fortifiers for feeding tolerance in premature infants

Background: Human milk is the ideal food for most babies, particularly for infants born prematurely. However, premature infants require fortification of human milk to meet the higher nutritional needs of their developmentally expected intra-uterine growth rates. Studies have shown that premature infants who are fed fortified breast milk have increased weight gain, length and head circumference, as well as improved bone mineralization. Premature infants who receive breast milk without fortification are at risk for extra-uterine growth retardation with lower growth rates and compromised neurodevelopmental outcomes. The two most commonly used commercially available liquid human milk fortifiers (HMF) are Enfamil HMF Acidified Liquid (Mead Johnson) and Similac HMF Concentrated Liquid (Abbott Nutrition). There are differences in the nutritional composition of each, as well as in the methods used to reduce bacterial content to safe levels. There is some debate amongst NICU clinicians about feeding tolerance and growth patterns of preterm infants whose human milk diet is fortified with either of these HMFs. Objectives: The objective of the study was to compare the feeding tolerance of preterm infants whose human milk diet was fortified with Enfamil HMF versus Similac HMF. Methods: This is an ongoing prospective, unblinded randomized controlled, single-center study being conducted at a Level IV NICU. The study population consisted of preterm infants born at < 35 weeks or < 1800 grams who were fed only human milk. When infants reach 100 mL/kg/day of feeds, Enfamil or Similac HMF was randomly assigned and added to their feeds. Subjects were stratified into 2 weight groups of < 1000 grams and >1000 grams with a target of 20 infants for each group. The study period began 1 week before and 2 weeks after initiation of HMF. Feeding intolerance was defined per unit protocol as an incidence where feeds were held due to abdominal distention, excessive gastric residuals, emesis or diarrhea. Feeding intolerance, demographic and morbidity data were analyzed. Anthropometric data were collected for later analysis. Results: Data from the first 52 study participants were analyzed. Twenty six infants received Enfamil HMF and 26 received Similac HMF. There were no statistically significant differences between the groups in gestational age at birth, birth weight, days of mechanical ventilation, incidence of NEC or sepsis, or in length of stay. Infants who received Enfamil HMF had feedings held for intolerance an average of 6.4 days while infants who received Similac HMF had feedings held an average of 3.4 days; however, the difference did not reach significance (p=0.2597). Conclusion: In this small study of two commercially available HMFs, preterm infants fed human milk fortified with Enfamil HMF were found to have trend towards more feeding intolerance than infants who received Similac HMF, but the trend did not reach statistical significance.