Pregnant women had an increased risk of 2.11 (95% CI: 1.20–3.73) for GDM in obesity group and of 1.64 (95% CI: 1.17–2.30) for CS in the overweight group with MTHFR A1298C AA genotype and 2.40 (95% CI: 1.28–4.47) for GDM in the obesity group and 1.98 (95% CI:1.38–2.85) for CS in the overweight group with MTHFR CT + TT genotype. The gene discussed is MTHFR; the disease is gestational diabetes.