Body Composition in Very Preterm Infants: Role of Neonatal Characteristics and Nutrition in Achieving Growth Similar to Term Infants

Abstract

Background: The identification of factors involved in the postnatal growth of preterm infants will help achieve growth similar to that of term infants. Objectives: As per protocol: to compare body composition in very preterm infants at term-corrected age (TCA) with that in term infants, and to explore relationships between neonatal characteristics and body composition in preterm infants. Methods: Anthropometry, nutritional characteristics, and neonatal outcomes were prospectively collected in 26 preterm (<29 weeks) and 33 term (37-40 weeks) infants. Body composition using dual-energy X-ray absorptiometry (DXA) was measured at TCA in preterm infants and between days 7 and 10 in term infants. Results: Parenteral nutrition in preterm infants provided a mean of 2.9 ± 0.2 and 2.1 ± 0.5 g/kg/day of intravenous amino acids and lipids, respectively, during the first week of life. The mean weight gain velocity from birth to DXA assessment was 12.1 ± 1.4 g/kg/day. Compared with term infants, preterm infants at TCA were shorter and lighter, with a smaller head circumference, a lower weight estimated by DXA (2,960 ± 552 vs. 3,843 ± 377 g), and increased skinfold thicknesses. Fat mass percent (13.9 ± 5.4%) and lean mass percent (84.7 ± 5.6%) in preterm infants were similar to those in term infants (14.7 ± 3.5 and 83.5 ± 3.6%, respectively). Neonatal weight gain velocity in preterm infants was positively associated with lean mass (grams). Conclusion: Subcutaneous fat is increased in preterm infants. Higher protein intake in preterm infants might increase weight gain velocity and achieve a lean mass comparable to that of term infants.