Epigenome-wide association study of maternal hemoglobin A1c in pregnancy and cord blood DNA methylation.

Gestational hyperglycemia is associated with adverse perinatal outcomes and long-term offspring metabolic programming, likely through dysregulation of DNA methylation (DNAm). We tested associations between maternal HbA1c and cord blood DNAm among 412 mother-child pairs in the genetics of glucose regulation in gestation and growth (Gen3G) and implemented Mendelian randomization to infer causality. We sought replication in an independent sample from Healthy Start. Higher second trimester HbA1c levels were associated with lower DNAm at cg21645848 (p = 3.9 × 10) near . Mendelian randomization and replication analyses showed same direction of effect between HbA1c and DNAm at cg21645848, but did not reach statistical significance. We found that higher maternal glycemia reflected by HbA1c is associated with cord blood DNAm at , a gene related with inflammatory pathways.