TCF7L2 and gestational diabetes: Several genes, such as the transcription factor 7-like 2 (TCF7L2) gene, the haematopoietically expressed homeobox gene (HHEX), the adiponectin, C1Q, and collagen domain containing (ADIPOQ) gene, and the vascular endothelial growth factor A (VEGFA) gene, are expressed in major tissues contributing to GDM, including the placenta.