Metals are involved in
glucose metabolism, and some may alter glycemic regulation. However, joint effects of essential and non-essential metals on
glucose concentrations during pregnancy are unclear. This study explored the joint associations of pregnancy exposures to essential (
copper,
magnesium,
manganese,
selenium,
zinc) and non-essential (
arsenic,
barium,
cadmium,
cesium, lead,
mercury) metals with gestational
glucose concentrations using 1,311 women enrolled 1999-2002 in Project Viva, a Boston, MA-area pregnancy cohort. The study measured erythrocyte
metal concentrations from 1st trimester blood samples and used
glucose concentrations measured 1 h after non-fasting 50-gram
glucose challenge tests (GCT) from clinical
gestational diabetes screening at 26-28 weeks gestation. Bayesian Kernel Machine Regression (BKMR) and quantile-based g-computation were applied to model the associations of
metal mixtures-including their interactions-with
glucose concentrations post-GCT. We tested for reproducibility of BKMR results using generalized additive models. The BKMR model showed an inverse U-shaped association for
barium and a linear inverse association for
mercury. Specifically, estimated mean
glucose concentrations were highest around 75th percentile of
barium concentrations [2.1 (95% confidence interval: -0.2, 4.4) mg/dL higher comparing to the 25th percentile], and each interquartile range increase of erythrocyte
mercury was associated with 1.9 mg/dL lower mean
glucose concentrations (95% credible interval: -4.2, 0.4). Quantile g-computation showed joint associations of all metals, essential-metals, and non-essential metals on gestational
glucose concentrations were all null, however, we observed evidences of interaction for
barium and lead. Overall, we found early pregnancy
barium and
mercury erythrocytic concentrations were associated with altered post-load
glucose concentrations in later pregnancy, with potential interactions between
barium and lead.