In addition, for children, MTHFR 677 TT and CT polymorphisms together were protective against leukemia (RR = 0.96, 95% confidence interval [CI = 0.93, 0.99], p = .0154), while CC wildtype was associated with increased risk of leukemia (RR = 1.04, 95% CI [1.01, 1.08], p = .0139) (Table 1A). This evidence concerns the gene MTHFR and leukemia.