Several studies confirmed that hydroxymethylation, a new epigenetic modification, was involved in the modulation of cell migration‐related genes.[64, 65, 66] An in vitro report showed that knockout of DNA hydroxymethylase reduced Nrg1 expression in prostate cancer cells.[67] By contrast, overexpression of DNA hydroxymethylase elevated Erbb4 abundance in hepatocellular carcinoma cells.[68] In this study, we found that 5hmC content at one CpG site (located on chr1: 32009246) in Nrg1 gene was diminished in fetal forebrain from the 1‐NP group. The gene discussed is ERBB4; the disease is hepatocellular carcinoma.