MTHFR and male infertility: Overall, the results revealed a significant association between the MTHFR C677T polymorphism and Chinese male infertility risk (T vs. C: OR = 1.47, 95%CI = 1.32–1.63; TT + CT vs. CC: OR = 1.51, 95%CI = 1.30–1.77; TT vs. CC: OR = 2.08, 95%CI = 1.68–2.58; TT vs. CT+CC: OR = 1.58, 95%CI = 1.31–1.90) (Figs 2–5).