Environmental Exposure to Toxic Metals and Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Background: Exposure to toxic metals have been inconsistently associated with the risk of gestational diabetes mellitus (GDM). We aimed to perform a systematic review and meta-analysis of epidemiological studies to examine the associations of exposure to arsenic, cadmium, lead, and mercury with GDM. Methods: PubMed, Web of Science, and Embase were searched for epidemiological studies reporting associations of arsenic, cadmium, lead, and mercury with risk of GDM up to 1 September, 2020. A random-effects model was used to calculate the pooled odds ratios (ORs) and 95% confidence intervals (CIs). Findings: Eleven studies, including 2867 GDM cases among 34760 participants, met the inclusion criteria. The pooled OR for the highest versus lowest category of arsenic was 1·36 (95% CI: 1·06, 1·75) for GDM. No significant associations between exposure to cadmium, lead, and mercury and risk of GDM were observed, with corresponding ORs of 1·16 (95% CI: 0·93, 1·44), 1·17 (95% CI: 0·78, 1·74), 1·26 (95% CI: 0·87, 1·82), respectively. In subgroup analysis, exposure to cadmium was associated with an increased risk of GDM among studies with measurement of urinary cadmium (OR, 1·28; 95% CI: 1·08, 1·51). Interpretations: This meta-analysis suggested a positive association between exposure to arsenic and risk of GDM. In addition, urinary cadmium was associated with an increased risk of GDM. Improved understanding of the effects of toxic metals on GDM may promote early identification of women with increased risk of GDM. Funding: This research was funded by the China postdoctoral Science Foundation (2019M662646) and the National Key R&D Program of China (2019YFC1605102). Declaration of Interests: All other authors declare no competing interests.