Nutrition, growth and body composition in moderate to late preterm babies

Abstract

Moderate to late preterm (MLPT; 32+0 to 36+6 weeks’ gestation) babies account for over 80% of preterm births worldwide and are increasingly recognised as being at an increased risk of mortality, neurodevelopmental delays and later cardiometabolic complications. Despite this, there is limited literature to support standardised nutrition guidelines during hospital admission after birth, resulting in significant variation in clinical practice. The primary aim of this thesis was to investigate associations between nutritional intake during hospital admission and growth and body composition outcomes at discharge and at 4 months’ corrected age (CA) in MLPT babies. This research is a secondary cohort analysis of the DIAMOND trial, a multicentred, randomised, controlled, factorial-design study of 532 MLPT babies admitted to 5 neonatal units (NNU) across New Zealand. Nutritional intakes were collected until discharge or 28 days, and growth and body composition were assessed at discharge and 4 months’ CA. Relationships between growth and body composition and nutritional intake were analysed using Pearson correlation coefficients and multiple linear regression models. Many associations were observed with a variety of nutrients, especially with outcomes at discharge. However, few remained at 4 months’ CA. Key findings included associations between total and enteral protein during hospital admission and increased weight z-score change (p = 0.02) and reduced fat mass percentage at 4 months’ (p = 0.02). Interestingly, total and enteral fat had the strongest associations, increasing fat mass percentage at discharge (p = 0.0009) but at 4 months’ CA, increasing fat-free mass percentage (p = 0.002), fat-free mass (p = 0.02), and change in head circumference (HC; p = 0.008 and 0.007, respectively) z-score. EP ratios within recommended ranges were associated with reduced fat mass outcomes at 4 months’, particularly in the moderate preterm (MP) cohort, reducing fat mass percentage (p = 0.02), fat mass (p = 0.04), fat mass z-score (p = 0.04) and fat mass index (p = 0.04). Intravenous (IV) fluids were not associated with enhanced growth or increasing fat-free mass and in some cases were associated with reduced growth with prolonged use. This data suggests that a prompt transition to full enteral feeding, coupled with adequate and balanced nutritional intake during NNU admission, benefits growth and body composition in MLPT babies. Future research should investigate the causal role of EP ratios in altering growth and body composition and explore the longitudinal outcomes in this population of babies.