However, subgroup analysis stratified by region revealed a significant association between the MTHFR gene C677T polymorphism and an increased risk of GDM only among the southern population in the allele model (OR=1.62, 95%:0.92-2.85, P=0.09; I2 = 91%, P<0.001), homozygote model (OR=2.22, 95%:1.28-3.83 P=0.004; I2 = 88%, P<0.001), heterozygote model (OR=1.17, 95%:0.88-1.56, P=0.28; I2 = 79%, P<0.001), dominant model (OR=1.43, 95%:1.03-1.98, P=0.03; I2 = 87%, P<0.001) and recessive model (OR=1.97, 95%:1.22-3.19, P=0.006; I2 = 87%, P<0.001). This evidence concerns the gene MTHFR and gestational diabetes.