MTNR1B and gestational diabetes: Genetic predisposition also plays a role: polymorphisms in genes such as transcription factor 7-like 2 (TCF7L2), melatonin receptor 1B protein (MTNR1B), insulin receptor substrate 1 (IRS1), potassium voltage-gated channel subfamily Q member 1 (KCNQ1), among others, have been associated with impaired β-cell function, insulin secretion, and predisposition to GDM [13,14,15].