Associations between Prenatal Mercury Exposure from Rice Consumption and Foetal Growth: A Cross-Sectional Study

The effect of prenatal Hg exposure on foetal development remains unclear, and the role of rice consumption as a dietary exposure source warrants further study. This study measured THg concentrations in maternal venous blood, placental tissue, and cord blood from 111 mother-infant pairs. Overall, THg exposure levels in this population were relatively low; however, pregnant women who consumed home-grown rice exhibited higher Hg concentrations than those who consumed market-purchased rice. After adjusting for covariates, Hg exposure was negatively associated with birth weight Z-score (BWz) and biparietal diameter Z-score (BPDz). Restricted cubic spline analysis further revealed a nonlinear relationship between cord blood THg and BWz, as well as a similar pattern between maternal THg and placental 5-methylcytosine (5mC) levels. Our findings suggest that prenatal Hg exposure may be associated with foetal growth outcomes and placental epigenetic alterations in a population where rice represents an important dietary source of MeHg. Given the cross-sectional design, causal inference is limited, and the findings should be interpreted with caution and not be overgeneralized. Further longitudinal studies in diverse populations are warranted to confirm these associations and clarify underlying mechanisms.