Unfortunately, the two available North American studies addressing the contribution of MTHFR 677C>T and/or MTRR 66A>G polymorphisms to the maternal risk for having a child with DS were published in 1999 and 2000 (James et al., 1999; Hobbs et al., 2000) and therefore, despite that both observed significant associations between the studied polymorphisms and maternal risk for DS, women enrolled in those studies were mainly collected from 1989 to 1998 and are unlikely to have benefited from the fortification (Hobbs et al., 2000). This evidence concerns the gene MTHFR and Dravet syndrome.