MTR and Dravet syndrome: Similarly, Biselli et al. (2008b) observed that the presence of three or more variant alleles among MTHFR 677C>T, MTHFR 1298A>C, MTR 2756A>G, and RFC1 80G>A, resulted in a 1.7-fold increase in maternal risk for a DS birth (Biselli et al., 2008b), while Brandalize et al. (2010) analyzed the genotypes generated by the following polymorphisms: MTR 2756A>G, MTRR 66A>G, CBS 844ins68, and RFC1 80G>A, observing that the OR for having a child with DS ranged from 4.8 to 6.9 depending on the number of risk genotypes considered (Brandalize et al., 2010).