BACKGROUND: In recent years, pro-, pre- and synbiotics have been suggested to positively influence the growth outcomes of infants and children. However, the findings have been inconsistent. This umbrella meta-analysis was conducted to evaluate this effect. METHODS: The PubMed, Web of Science and Scopus databases were systematically searched until June 2024 to identify relevant studies. Weight gain, length gain, head circumstance (HC) gain, body mass index (BMI) as well as weight-for-height (WHZ), height-for-age (HAZ), weight-for-age (WAZ) and BMI-for-age (BMIAZ) Z-scores were considered as the outcomes. Standardised mean differences (SMD) along with the 95% confidence interval (CI) were utilised to estimate the overall effect size. Subgroup analyses were conducted to identify the sources of heterogeneity among the studies. RESULTS: We included 26 meta-analyses, which encompassed a total of 72 285 participants. The pooled umbrella analysis revealed positive effects of pro-, pre- and synbiotics on weight gain (SMD = 0.17, 95% CI: 0.09-0.25) and height gain (SMD = 0.10, 95% CI: 0.01-0.19) in both healthy individuals and preterm infants, although significant heterogeneity was observed across the studies (p <
0.001). Furthermore, the subgroup analyses indicated very weak evidence for an increase in BMI and WAZ following microbiome-based interventions. CONCLUSION: Supplementation with pro-, pre- and synbiotics has the potential to enhance weight and height gain in infants and children. Additional large-scale studies are needed to confirm their clinical applications.