TCF7L2 and gestational diabetes: Regarding the overall architecture of genetic susceptibility of GDM, it should be recognized that many of the gene variants we report here (MTNR1B, CDKAL1, SLC30A8, TCF7L2 and potentially exerts similar effect) were reported to be associated with a reduced first phase insulin secretion, while the second-phase insulin secretion remained intact [34, 44–47].