Therefore, under these conditions, the presence of mutations in important genes for β-cell formation/functionality such as PAX4 (MODY9), HMG20A and PAX8, that may remain undiagnosed since their effects will not be revealed in the absence of environmental stressors, could trigger an inadequate response under situations of increased insulin demand such as pregnancy, triggering the development of GDM. The gene discussed is HMG20A; the disease is gestational diabetes.