MTHFR and male infertility: Overall, we find the MTHFR 677C>T variant genotype were significantly associated with male infertility risk based on both fixed effects and random effects models, and which was consistent with the results of Tüttelmann et al. [15], Gupta et al. [16] and Wu et al. [17], but inconsistent with the results of Wei et al. [18] and Weiner et al. [19].