Associations of Heavy Metals and Trace Elements with Gestational Diabetes Mellitus in the Boston Birth Cohort

We investigated the associations of pregnancy levels of heavy metals and trace elements with the risk of gestational diabetes mellitus (GDM). Participating pregnant women were from the Boston Birth Cohort. We measured levels of mercury, lead, cadmium, selenium, and manganese in maternal red blood cells collected after delivery. We verified the GDM diagnosis using ICD codes, medication history, and plasma glucose profile abstracted from medical records. We used modified Poisson regression and Bayesian kernel machine regression models to examine associations of metals and elements, individually and as a mixture, with GDM. We stratified the analyses by race and ethnicity. Among 1256 pregnant women, 58% were non-Hispanic Black and 22% were Hispanic. Overall, each doubling of mercury and manganese levels was associated with 1.14 (95% CI: 1.01-1.28) and 0.65 (95% CI: 0.50-0.84) times the risk of GDM, respectively. In the race- and ethnicity-stratified analyses, the mercury-GDM association was stronger among Black women, and higher selenium levels were associated with higher GDM risk only among Hispanic women (P_interaction = 0.01). In conclusion, women with higher mercury or lower manganese levels during pregnancy were more likely to develop GDM. An increased GDM risk associated with higher selenium levels was observed only in Hispanic women.