Background: Knowledge of growth trajectories and their determinants early in life have particular implications for designing future interventions to promote healthy growth. This study aimed to identify the modifiable child and maternal correlates of longitudinal growth trajectories from birth to age 42 months.
Methods: Secondary analyses of pooled data from the Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program (n=540) and the InFANT Extend study (n=514) were conducted. Children’s height and weight were collected at birth, 3, 9, 18, and 42 months. Age- and gender-specific height, weight, and body mass index-for-age z-scores (HAZ, WAZ, and BAZ) were computed using World Health Organisation growth charts. Mixed effect modelling was performed to examine whether growth trajectories (changes in HAZ, WAZ and BAZ) from birth to age 42 months were influenced by birth weight, rapid weight gain (defined as an increase from birth to 9 months in WAZ ≥0.67) and maternal factors.
Results: Low birth weight infants had significantly lower HAZ, WAZ and BAZ than normal weight infants from birth to 42 months (P<0.001). Infants with rapid weight gain had significantly higher BAZ and WAZ, but not HAZ, when compared to those without rapid weight gain (P<0.01). Infants whose mothers were Australian born had higher HAZ than infants whose mothers were born overseas (P=0.02). Increased pre-pregnancy BMI was a significant predictor of changes in all three growth parameters (P<0.01). High maternal education was inversely associated with changes in WAZ and BAZ (P<0.01).
Conclusion: Our findings indicate that low birth weight, rapid weight gain, and several maternal factors are potential correlates of growth trajectories early in life. Recognising these early determinants provides the focus for the design of future intervention strategies to target most-at-risk groups for promoting healthy growth.