Although genetic variants in Transcription Factor 7-like 2 (TCF7L2) (9, 10), Peroxisome Proliferator Activated Receptor γ (PPARγ) (11), Insulin Receptor Substrate 1 (IRS1), Melatonin Receptor 1B (MTNR1B) (12, 13), Glucokinase (GCK), Insulin Like Growth Factor 2 mRNA Binding Protein 2 (IGF2BP2), Potassium Voltage-Gated Channel Subfamily J Member 11 (KCNJ11), Potassium Voltage-Gated Channel Subfamily Q Member 1 (KCNQ1) (14, 15), and CDK5 Regulatory Subunit Associated Protein 1 Like 1 (CDKAL1) are involved in both GDM and T2DM risk, their effect sizes for the risk vary in different genes. The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.