Placental cellular composition and umbilical cord tissue metal(loid) concentrations: A descriptive molecular epidemiology study leveraging DNA methylation.

The placenta is a mixture of cell types, which may regulate maternal-fetal transfer of exogenous chemicals or become altered in response to exposures. We leveraged placental DNA methylation to characterize major constituent cell types and applied compositional data analysis to test associations with non-essential metal(loid)s measured in paired umbilical cord tissue (N = 158). Higher proportions of syncytiotrophoblasts were associated with lower arsenic, whereas higher proportions of Hofbauer cells were associated with higher cadmium concentrations in umbilical cords. These findings suggest that placental cellular composition influences amounts of metal(loid)s transferred to the fetus or that prenatal exposures alter the placental cellular makeup.