MTNR1B and gestational diabetes: The five key genes associated with GDM in general are transcription factor 7-like 2 (TCF7L2) [149,150]; melatonin receptor 1B (MTNR1B) [151,152]; CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1) [122,153]; potassium voltage-gated channel, KQT-like subfamily, member 1 (KCNQ1) [154,155]; and insulin receptor substrate-1 (IRS1) [147,156,157].