MTRR and vitamin B12 deficiency: As accumulating evidence suggests that periconceptional folic acid supplementation could be preventive against CHD, Van Beynum and co-authors demonstrated that maternal SNPs in methionine synthase reductase (MTRR), coupled with elevated plasma methylmalonic acid concentrations—an indicator of vitamin B12 deficiency—may be indicative of an elevated risk of CHD in offspring [46].