MTHFR and fetal growth restriction: CHR: Chromosome, SNP: Single nucleotide polymorphism, FGR: Fetal growth restriction, OR: Odds ratio, CI: Confidence interval, MTR: 5,10-methylenetetrahydrofolate reductase, MTRR: Methionine synthase reductase, SHMT1: Serine hydroxymethyl transferase 1, TYMS: Thymidylate synthetase. Logistic regression was used. Statistically significant results were selected taking into account the permutation test (1000 permutations were performed)