IGF1 and gestational diabetes: One mechanism that could be implicated in fetal overgrowth in pregnant women with GDM is that low levels of maternal adiponectin, combined with increased levels of insulin growth factor 1 (IGF-1), could cause an increased expression of glucose transporter protein 1 (GLUT-1) via heightened activation of insulin/IGF-1 signaling in the placenta of these women.