title: Determinants of arm muscle and fat accretion during the first postnatal month in preterm newborn infants.
abstract: We measured arm muscle and fat areas in 22 preterm appropriate for gestational age infants at birth (mean +/- 1 SD birth weight: 1,640 +/- 484 g; gestational age: 31 +/- 2 weeks). Birth arm muscle and fat areas correlated significantly with gestational age (arm muscle: r = 0.86; p less than 0.001; arm fat: r = 0.75; p less than 0.001) and with birth weight. Deviations of birth weights from gestational age means (birth weight z-scores) were related more to variations in arm muscle area (r = 0.69; p less than 0.001) rather than arm fat area (r = 0.44; p = 0.04). Sixteen infants were followed over 4 weeks. They were most physiologically unstable (mean Physiologic Stability Index score = 5.3 +/- 3.5) during the first postnatal week when they also all lost weight. Their mean arm muscle area decreased significantly during the first week by greater than 10%, whereas the mean arm fat area remained unchanged. First week arm muscle losses were directly correlated with the lack of protein intake (r = 0.52; p less than 0.05). The regression equation predicted a protein intake of 4.06 g/kg/day (95% confidence interval: 2.3-6.4) to prevent first week muscle loss. Enteral intake and weight gain were established after week 1, accompanied by a significant reduction in physiologic instability (PSI score = 1.9 +/- 1.9; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, University of Minnesota School of Medicine, Children's Hospital of St. Paul, Minneapolis.
authors.forename: M K
authors.initials: MK
authors.lastname: Georgieff
authors.forename: U M
authors.initials: UM
authors.lastname: Amarnath
authors.forename: M M
authors.initials: MM
authors.lastname: Mills
mesh_terms: D000273:Adipose Tissue / Q000254:growth & development*; D001132:Arm / Q000254:growth & development*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D024510:Muscle Development