Bivariate analysis of placental global DNA methylation in association with prenatal exposure to fine particulate air pollution (PM
). PM2.5 exposures (μg/m3) are presented with spearman correlation coefficients for the whole pregnancy (A) and first trimester (B). In panel C, the association between average PM2.5 concentrations and placental global DNA methylation is given. The effect of the average concentrations over 91 days periods was estimated using restricted cubic splines with 5 knots located at the 5th, 25th, 50th, 75th and 95th percentiles.