ROC curve analysis demonstrated that afamin (AUC = 0.826, P < 0.001), FGF21 (AUC = 0.877, P < 0.001), and their combined assessment (AUC = 0.9, P < 0.001) were strong predictors of GDM development at 1st trimester before the development of the disease than expectant mothers with normal pregnancy. This evidence concerns the gene FGF21 and gestational diabetes.