We investigated associations of prenatal socioeconomic status (SES) with DNA methylation at birth, and to explore persistence of associations into early (∼3 years) and mid-childhood (∼7 years) among 609 mother-child pairs in a Boston-area prebirth cohort. First, we created a prenatal SES index comprising individual- and neighborhood-level metrics and examined associations of low (lowest 10%) versus high (upper 90%) SES with genome-wide DNA methylation in cord blood via the Infinium HumanMethylation450 BeadChip. Next, we evaluated persistence of associations detected in cord blood with DNA methylation of the same CpG sites measured in peripheral leukocytes in early- and mid-childhood. Low prenatal SES was associated with methylation at CpG sites near , , and . The relationship with persisted into early childhood.