MTHFR and neural tube defect: Pooled data showed that the MTHFR C677T SNP was significantly associated with an increased risk of NTD in all of the five genetic models, i.e., allele (T vs. C: OR = 0.73, 95% CI 0.67–0.79, p ≤ 0.0001), recessive (TT vs. TC + CC: OR = 0.70, 95% CI 0.62–0.78, p ≤ 0.0001), homozygote (TT vs. CC: OR = 0.55, 95% CI 0.46–0.64, p ≤ 0.00001), heterozygote (TT vs. TC: OR = 0.76, 95% CI 0.67–0.86, p ≤ 0.01), dominant (TT + TC vs. CC: OR = 0.64, 95% CI 0.56–0.74, p ≤ 0.0001) (Figure 1).