Plasma levels of trace element status in early pregnancy and the risk of gestational diabetes mellitus: A nested case-control study

Purpose: We investigated the impacts of plasma levels of magnesium (Mg), zinc (Zn), calcium (Ca), iron (Fe), copper (Cu), selenium (Se), and chromium (Cr) on GDM risk and the potential mediation effect of blood glucose levels on the relationship between trace elements and GDM risk. Methods: This nested case-control study was based on data from a birth cohort study conducted in Wuhan, China in 2013-2016. A total of 305 GDM cases and 305 individually-matched controls were included in the study. Conditional logistic regression models were used to estimate the associations between plasma trace element concentrations and GDM risk. A mediation analysis was conducted to explore whether blood glucose levels act as a mediator between trace element levels and GDM risk. Results: An IQR increment in plasma levels of Fe and Cu was associated with a significant increase in GDM risk [OR = 2.04 (95 % CI 1.62, 2.57) and OR = 1.52 (95 % CI 1.25, 1.82)], respectively. On the other hand, an IQR increment in plasma levels of Zn and Ca was associated with a significant decrease in GDM risk [OR = 0.55 (95 % CI 0.43, 0.71) and OR = 0.72 (95 % CI 0.56, 0.92)], respectively. The mediation analysis showed significant mediation of the association between Cu and GDM risk via the FBG (%mediated: 19.27 %), 1 h-PBG (12.64 %), 2h-PBG (28.44 %) pathways. Conclusions: Plasma levels of Zn and Ca were negatively associated with GDM risk, while Fe and Cu were positively associated. Blood glucose levels act as a mediator between plasma trace element exposures and GDM risk.