A systematic review and meta-analysis of the association between exposure to potentially toxic elements and gestational diabetes mellitus

Potentially toxic elements (PTEs), including heavy metal exposures, have been associated with numerous negative pregnancy and birth outcomes. However, the association between PTE exposure and gestational diabetes mellitus (GDM) has not yet undergone a comprehensive systematic review. Consequently, this study undertook the first-ever systematic review and meta-analysis of observational studies concerning this association. All relevant articles published in English were searched in Scopus, PubMed, and Web of Science until November 6, 2023, adhering to the MOOSE guidelines. The quality of retrieved studies was evaluated based on the Gascon et al. method. The meta-analysis of association estimates was performed using random effects meta-analysis. Egger’s regression was employed to evaluate publication bias. In total, 16 articles (n = 116,728 participants) were included in our review, with 11 eligible for meta-analysis. Quality assessment categorized five studies (31%) as excellent, nine studies (56%) as good, and two studies (13%) as fair. Maternal high levels of Hg during pregnancy were associated with an increased risk of GDM (for each one-quartile increase in Hg: 1.20, 95% CI 1.08, 1.31), while serum Cd levels during the second trimester were associated with a lower risk of GDM (for each one-quartile increase in Cd: 0.76, 95% CI 0.65, 0.87). Furthermore, exposure to Pb was not associated with higher risk of GDM. In summary, our comprehensive review and meta-analysis underscore the possible negative influence of Hg exposure on GDM.