Exposure to organophosphorus and organochlorine pesticides, perfluoroalkyl substances, and polychlorinated biphenyls in pregnancy and the association with impaired glucose tolerance and gestational diabetes mellitus: The MIREC Study.

•Environmental chemical exposure may be a risk factor for gestational diabetes.•We examined several types of chemicals in relation to gestational diabetes.•None of the chemicals was associated with increased gestational diabetes risk.•Two organophosphorus pesticide metabolites were associated with reduced risk.•These findings require further investigation.