Objective: The aim of this study was to investigate the effects of prenatal heavy metal (arsenic, cadmium, manganese) exposure on infant neurodevelopment through a systematic review and meta-analysis, elucidating the toxicological mechanisms and dose–response relationships for consideration in environmental risk assessment. Methods: Following the PRISMA guidelines, systematic searches were conducted in PubMed, Embase, and other databases, ultimately resulting in 17 observational studies involving 6907 participants. Results: Arsenic (As): A 50% increase in arsenic exposure was associated with a reduction of 0.51 points in the Mental Development Index (MDI; 95% CI: −1.43 to 0.4) and 0.15 points in the Psychomotor Development Index (PDI; 95% CI: −0.96 to 0.65). However, these results did not achieve statistical significance (p > 0.05). Cadmium (Cd): Prenatal cadmium exposure significantly decreased the Full-Scale Intelligence Quotient (FSIQ) in children aged 5–9 years. A 50% increase in cadmium exposure resulted in a 0.44-point drop in the FSIQ (95% CI: −0.67 to −0.21, p < 0.05), with stable effects (I² = 0%). Manganese (Mn): Manganese exposure showed a negative association with the MDI (β = −0.11) and PDI (β = −0.18). However, a high degree of heterogeneity was observed (I² = 20.89–73.35%), and some studies suggested potential risks even at low exposure levels. Sensitivity analyses indicated that the heterogeneity in the arsenic and manganese results mainly stemmed from individual study differences (e.g., sample characteristics), whereas the cadmium effects were consistent. Conclusions: Prenatal heavy metal exposure (notably cadmium) adversely impacts neurodevelopment, even at low doses. Future research should prioritize critical exposure windows, mixed effects, and sex-specific vulnerabilities. Strengthening environmental monitoring and prenatal guidelines is crucial to mitigate developmental risks.

Background and Objectives: The escalating prevalence of gestational diabetes mellitus (GDM) and the limitations associated with utilizing body mass index (BMI) as a predictive measure underscore the imperative need for identifying an optimal early pregnancy predictor. Such a predictor not only mitigates the risk of GDM but also allows for timely implementation of interventions. Materials and Methods: This meta-analysis aimed to explore the association between visceral adipose tissue (VAT) depth and the risk of GDM. A thorough search of PubMed, Embase, and Web of Science databases was conducted up to 30 September 2023. The analysis employed a random-effects model to assess the relationship between VAT depth and the likelihood of GDM. Results: The inclusion criteria encompassed seven studies involving 1315 women, including 225 diagnosed with GDM. Significantly lower VAT depth was observed in the non-GDM group in comparison to the GDM group (Standardized Mean Difference [SMD]: 0.84; 95% Confidence Interval [CI]: 0.52–1.15; p < 0.001). Substantial statistical heterogeneity was noted among studies (I² = 72.88%, p = 0.001). Through meticulous sensitivity and subgroup analyses, the source of heterogeneity was identified and thoroughly discussed. Subgroup analyses suggest that different GDM diagnostic criteria and VAT definitions all indicate higher VAT depth in GDM patients during early pregnancy. Conclusions: Our findings propose that, during the first trimester, GDM patients exhibit higher VAT depth compared to non-GDM women, highlighting VAT depth as a potential predictive factor for GDM in early pregnancy. This study contributes valuable evidence to the growing body of knowledge surrounding novel predictors for GDM, emphasizing the importance of early intervention strategies.