Since macrocephaly is more strongly related to ASD than to intellectual disability (ID) [62] and many hcASD genes such as CHD8 and WDFY3 cause dysregulation of proliferation and brain overgrowth [193, 177, 183], what other fetal mechanisms are altered by excess proliferation that lead to an ASD outcome? This evidence concerns the gene CHD8 and Macrocephaly.