Abstract
BACKGROUND: Early-life exposures might negatively affect fetal and infant development, predisposing children to obesity. This study aimed to systematically identify and evaluate risk factors for childhood obesity in preconception, pregnancy, and infancy, and assess their potential for future prediction and prevention strategies. METHODS: This systematic review (PROSPERO, CRD42022355152) included longitudinal studies from selected electronic databases published between inception and August 17th, 2022, identifying maternal, paternal, or infant risk factors from preconception until infancy for childhood obesity between 2 and 18 years. Screening and data extraction were conducted using standardized forms. We assessed risk factor quality on modifiability and predictive power using a piloted criteria template from ILSI-Europe-Marker-Validation-Initiative. FINDINGS: We identified 172 publications from observational and five publications from intervention studies involving n = 1,879,971 children from 37, predominantly high-income, countries. Average reported childhood obesity prevalence was 11.1%. Pregnancy and infancy risk factors were mostly studied. We identified 59 potential risk factors; 23 were consistently associated. Strongest risk factors were: higher maternal prepregnancy weight (n = 28/31 publications with positive associations), higher gestational weight gain (n = 18/21), maternal smoking during pregnancy (n = 23/29), higher birth weight (n = 20/28), large-size-for-gestational-age-at-birth (n = 17/18), no breastfeeding (n = 20/31), and higher infant weight gain (n = 12/12). Level of evidence was generally moderate due to unreliable exposure measurement, short follow-up/loss to follow-up, and risk of confounding. INTERPRETATION: We identified seven early-life risk factors, which were strongly associated with childhood obesity, and can contribute to future prediction and prevention strategies. These findings support the implementation of prevention strategies targeting these risk factors from a clinical and population perspective, where possible integrated with implementation studies.