Background/Aims: Despite the extensive research linking infant rapid weight gain (RWG) with later obesity risk, the examination of factors associated with RWG during infancy is scarce. This study examined the association between a broad range of child and maternal factors and RWG in the first year of life.
Methods: Data from seven Australian and New Zealand cohorts were used (INFANT, INFANT Extend, Barwon Infant Study, LIMIT, Healthy Beginnings, NOURISH, POI) (n=4534). Weight z-scores at birth and around one year of age were calculated using WHO growth charts. Infant RWG was defined as a change in weight z-score≥0.67 from birth to age one year. Multivariable logistic regression was used to assess the child and maternal determinants of infant RWG in each study. Meta-analysis was conducted to obtain pooled effect sizes.
Results: Boys were more likely to experience RWG (OR 1.38 95%CI 1.19, 1.60) than girls. Higher birth weight in kg (OR 0.09, 95%CI 0.04, 0.20) and greater gestational age in weeks (OR 0.69, 95%CI 0.48, 0.98) were associated with lower RWG risk. Children who were breastfed for≥ 6 months were less likely to experience RWG (OR 0.47, 95%CI 0.40, 0.50). Solid introduction after age 6 months was associated with lower RWG risk (0R 0.77, 95% 0.63, 0.94). In contrast, children of smoking mothers showed higher odds (OR 1.60, 95%CI 1.28, 2.01) of experiencing RWG than those of non-smoking mothers. No evidence of association was found for maternal age, education level, marital status, and pre-pregnancy BMI.
Conclusion: The current study contributes to the limited body of evidence on determinants and aetiology of RWG. Child sex, birth weight, gestational age, infant feeding and maternal smoking status were identified as significant determinants of infant RWG. The findings provide valuable insights for obesity prevention policy and practice regarding the key factors to target and intervene.