TET1, TET2 and TET3, are involved in regulation of DNA hydroxymethylation.[69] An earlier study showed that TET1, TET2 and TET3 were highly expressed in fetal neocortex.[70] Recently, an epidemiological study observed autism phenotypes in patients with human Mendelian disorder with TET3 deficiency.[71] Moreover, TET1‐deficient mice exhibited autism‐like behaviors.[72] In this study, we detected TETs expression and TETs activity in fetal forebrain. This evidence concerns the gene TET3 and autism.