Growth trajectories in early childhood, their relationship with antenatal and postnatal factors, and development of obesity by age 9 years: results from an Australian birth cohort study

BACKGROUND: In an era where around one in four children in the United Kingdom, the United States, and Australia are overweight or obese, the development of obesity in early life needs to be better understood. We aimed to identify groups of children with distinct trajectories of growth in infancy and early childhood, to examine any association between these trajectories and body size at age 9, and to assess the relative influence of antenatal and postnatal exposures on growth trajectories. DESIGN: Prospective Australian birth cohort study. SUBJECTS AND METHODS: In total, 557 children with serial height and weight measurements from birth to 9 years were included in the study. Latent class growth models were used to derive distinct groups of growth trajectories from birth to age 3(1/2) years. Multivariable logistic regression models were used to explore antenatal and postnatal predictors of growth trajectory groups, and multivariable linear and logistic regression models were used to examine the relationships between growth trajectory groups and body size at age 9 years. RESULTS: We identified four discrete growth trajectories from birth to age 3(1/2) years, characterised as low, intermediate, high, or accelerating growth. Relative to the intermediate growth group, the low group had reduced z-body mass index (BMI) (-0.75 s.d.; 95% confidence interval (CI) -1.02, -0.47), and the high and accelerating groups were associated with increased body size at age 9 years (high: z-BMI 0.70 s.d.; 95% CI 0.49, 0.62; accelerating: z-BMI 1.64 s.d.; 95% CI 1.16, 2.11). Of the antenatal and postnatal exposures considered, the most important differentiating factor was maternal obesity in early pregnancy, associated with a near quadrupling of risk of membership of the accelerating growth trajectory group compared with the intermediate growth group (odds ratio (OR) 3.72; 95% CI 1.15, 12.05). CONCLUSIONS: Efforts to prevent childhood obesity may need to be embedded within population-wide strategies that also pay attention to healthy weight for women in their reproductive years.