Methylmercury (CH3Hg) is a highly specific irreversible selenoenzyme inhibitor with toxic effects occurring through disruption of selenium (Se) metabolism. Selenoenzymes prevent oxidative damage in brain tissues, regulate metabolic/endocrine functions, ensure energy balance, and are essential for supporting fetal and postnatal brain development. Damage from CH3Hg exposures will occur if dietary Se intakes and tissue reserves fail to offset Hg-dependent Se binding in the brain. Because ocean fish are rich in Se, their consumption prevents rather than causes this conditioned Se deficiency. Concerns regarding dietary CH3Hg exposures were based on populations that eat marine mammals which contain more Hg than Se. In contrast, nearly all commercial ocean fish species contain more Se than CH3Hg, and their consumption is associated with numerous benefits to child and maternal health. Misunderstandings of Hg-associated risks deter many women from eating fish during pregnancy, thereby diminishing nutritional benefits to their children. Although most ocean fish are Se rich, Se levels in freshwater fish are variable, especially in Se-poor regions. Therefore, increased ocean fish consumption should be encouraged during pregnancy, particularly in regions with Se-poor populations.