BACKGROUND & AIMS: Scarce knowledge about the impact of metabolism-disrupting chemicals (MDCs) on steatotic liver disease limits opportunities for intervention. We evaluated pregnancy MDC-mixture associations with liver outcomes, and effect modification by folic acid (FA) supplementation in mother-child pairs. METHODS: We studied ∼200 mother-child pairs from the Mexican PROGRESS cohort, with 43 MDCs measured during pregnancy (estimated air pollutants, blood/urine metals or metalloids, urine high- and low-molecular-weight phthalate [HMWPs, LMWPs] and organophosphate-pesticide metabolites), and serum liver enzymes (ALT, AST) at ∼9 years post-parturition. Outcomes included elevated liver enzymes in children and established clinical scores for steatosis and fibrosis in mothers (i.e. , AST: ALT, FLI, HSI, FIB-4). Bayesian-weighted quantile sum regression assessed MDC-mixture associations with liver outcomes. We further examined chemical-chemical interactions and effect modification by self-reported FA supplementation. RESULTS: In children, many MDC-mixtures were associated with liver injury. Per quartile HMWP-mixture increase, ALT increased by 10.1% (95% CI 1.67%, 19.4%) and AST by 5.27% (95% CI 0.80%, 10.1%). LMWP-mixtures and air pollutant-mixtures were associated with higher AST and ALT, respectively. Air pollutant and non-essential metal/element associations with liver enzymes were attenuated by maternal cobalt blood concentrations (p-interactions <
0.05). In mothers, only the LMWP-mixture was associated with odds for steatosis (odds ratio = 1.53, 95% CI 1.01-2.28 for HSI >
36, and odds ratio 1.62, 95% CI 1.05-2.49 for AST:ALT <
1). In mothers and children, most associations were attenuated (null) at FA supplementation ≥600 μg/day (p-interactions <
0.05). CONCLUSIONS: Pregnancy MDC exposures may increase risk of liver injury and steatosis, particularly in children. Adequate FA supplementation and maternal cobalt levels may attenuate these associations. IMPACT AND IMPLICATIONS: The effects of environmental chemical exposures on steatotic liver diseases are not well understood. In a parallel investigation of mothers and children, we found that pregnancy exposures to metabolism-disrupting chemicals may increase the risk of liver injury and steatosis, especially in the child, and that these associations could be attenuated by higher folic acid and/or cobalt levels. These findings can inform policies to decrease environmental chemical pollution and contribute to the design of clinical interventions addressing the metabolic dysfunction-associated steatotic liver disease epidemic.