Factors Influencing Body Composition of Premature Infants at Term-Adjusted Age
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We investigated the influence of body size at birth, feeding of mother's milk versus formula, or standard-term formula versus energy- or nutrient-enriched formula on the growth and whole body bone mineral content (BMC), lean and fat mass (using dual-energy X-ray absorptiometry) of low-birth-weight (LBW) infants to term-adjusted age. LBW infants who were appropriate for gestational age were lighter and shorter than term-born infants (n = 46) but had a higher percent fat mass (19-28% vs. 15 +/- 7%). For LBW infants fed standard formula or mother's milk after hospital discharge, the mean BMC expressed either as a function of weight (17 +/- 2, 19 +/- 2 vs. 20 +/- 2 g/kg) or length (1.1 +/- 0.2, 1.1 +/- 0.2 vs. 1.5 +/- 0.2 g/cm) was more than 1 SD below term infant values. However, infants fed a nutrient-enriched formula from hospital discharge had BMC within 1 SD below term infants. Infants who were born small, compared to appropriate for gestational age, compared to infants of similar birth weight had lower percent body fat (16 +/- 6 vs. 19 +/- 5) and lower BMC (47 +/- 3 vs. 62 +/- 5 g) at term age. Both size at birth and diet influence patterns of growth and body composition in early life in very-low-birth-weight (VLBW) infants. The long-term significance of these variable growth patterns in VLBW infants in early life requires further investigation.