Growth and body composition changes in late preterm infants in the first months of life

The weight for length in late preterm infants assessed with bioelectrical impedance is positively associated with anthropometric variables

INTRODUCTION

The fat mass (FM) is greater in late preterm than full term infants at 1 month post birth, which may be an additional risk factor for metabolic syndrome in adulthood.

OBJETIVES

To evaluate body composition (BC) in late preterm infants using bioelectrical impedance analysis (BIA) to determine which anthropometric parameters are associated with BC. Our hypothesis was that weight-for-length is associated with the length-normalized fat mass index (FMI) at 1 year of life.

MATERIALS AND METHODS

We carried out a prospective cohort study in 2 groups: late preterm infants and full term infants. We obtained BC data by BIA. We calculated the fat mass (FM), FMI, fat-free mass (FFM) and length-normalized fat-free mass index (FFMI) at 1, 6 and 12 months of life. After, we assessed the association of the FMI with anthropometric parameters using multiple linear regression analysis.

RESULTS

The study included 97 late preterm and 47 full term infants, although at 12 months of life, the BC assessment was performed on 66 and 33 infants, respectively. Late preterm infants, compared to full term infants, had a higher FFM at 1 month (4013 vs 3524 g), a higher weight velocity at 6 months (5480 g versus 4604 g) and a lower FFM (7232 vs 7813 g) and FFMI (12.55 vs 13.26) at 12 months of life. The multivariate regression analysis showed that the weight-for-length z-core at 12 months was positively associated with the FMI at 12 months in all infants.

CONCLUSION

The weight-for-length z-score at 12 months is strongly associated with the FMI at 1 year of life. Further studies are needed to investigate whether an increment in this anthropometric parameter may modulate the risk of chronic diseases.

Effect of foetal and infant growth and body composition on respiratory outcomes in preterm-born children

Body composition and growth outcomes of preterm-born subjects have been studied by many researchers. In general, preterm-born children have lower height and weight especially in infancy. Despite showing potential for catch-up growth, they continue to lag behind their term counterparts in adolescence and adulthood. The various methods of studying body composition and the differing gestations and ages at which it is assessed may go some way to explaining the inconsistent results observed in different studies. In addition, there is a paucity of data on the effects of foetal and infant growth and of body composition on later respiratory outcomes. In largely term-born subjects, foetal growth and growth trajectories appear to have differential effects on later respiratory outcomes. Early weight gain in infancy appears to be associated with increased respiratory symptoms in childhood but catch-up growth in infancy appears to be associated with possible improved lung function status.

Linear growth and neurodevelopmental outcomes

Despite advances in care, preterm infants exhibit disproportionate growth and neurodevelopmental delay attributable to both nutritional and nonnutritional factors. These infants have prolonged linear stunting and decreased fat-free mass compared with their term counterparts. These 2 metrics index organ growth and development (including the brain) and protein accretion. Protein, along with carbohydrates, fats, and zinc, plays key roles in brain development, and deficiencies can lead to linear growth failure, abnormalities in the growth hormone axis, and developmental delay. Optimization of nutrition, including protein intake, decreasing inflammatory episodes, and enhancing the growth hormone axis will likely improve long-term outcomes.