FIGURE 1.

CpG-specific epigenome-wide association study results by maternal periconceptional folate source. A total 697,560 CpGs from the EPIC DNA-methylation array (Illumina) were included in multivariable linear regression analysis. (A) Quantile-quantile (QQ) plots demonstrating distribution of observed versus expected –log(10) raw P values for total, food, and supplemental periconceptional DFEs. Lambda values (λ) on plots represent estimation of genomic inflation, which was minimal across the 3 folate sources. (B) Volcano plot demonstrating –log(10) raw P value by regression coefficient. One significant DMP was identified in association with food folate and a second in association with supplemental folic acid intake. The hatched line represents FDR <0.05. Significant DMPs are positioned above the hatched line and are bolded, with associated gene names presented on the plot; unnamed DMPs are intergenic. DFE, dietary folate equivalent; DMP, differentially methylated probe; FDR, false discovery rate.