For all included studies, both generations, MTHFR 677TT and TT plus CT polymorphisms together were risk genotypes for CHD (RR = 1.30 and 1.07; 95% CI = 1.17–1.44 and 1.04–1.11) (Supplementary Table S2); and for subgroups of children (RR = 1.30 and 1.09; 1.14–1.48 and 1.04–1.14) (Table 2), parents (RR = 1.24 and 1.06; 1.09–1.41 and 1.01–1.011) (Supplementary Table S3a), and mothers (RR = 1.21 and 1.05; 1.04–1.39 and 1.00–1.11) (Supplementary Table S3b), while MTHFR 677TT homozygous polymorphism was the risk genotype for fathers (RR = 1.39, 1.02–1.91) (Supplementary Table S3c). This evidence concerns the gene MTHFR and coronary artery disorder.