Adrenomedullin (ADM) is a strong vasodilator peptide that was first identified in human pheochromocytoma and known to expressed in numerous cell types and believed to have pleiotropic impacts on pregnancy-related vascular adaptations and fetal growth. Mid-regional pro-adrenomedullin (MR-proADM) peptide which secreted in an equimolar concentration to ADM used to quantify ADM in plasma since it has longer half-life with more availability than ADM and for that reason the present study determine the serum MR-proADM level in the plasma of pregnant women with and without GDM and determine any potential correlation between MR-proADM and gestational diabetes mellitus (GDM) in an observational case–control study conducted on 90 pregnant women in the third trimester of pregnancy who were divided into two groups: 45 pregnant women with GDM as patient and 45 apparent healthy pregnant women without GDM as control and the levels of MR-proADM, and the diabetic markers that include fasting serum insulin (FSI), fasting blood glucose (FBG), glycosylated hemoglobin (HbA1c) and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were determined and results revealed that the serum levels of MR proADM were significantly higher in patients with GDM compared with those of controls, and also showed that MR proADM levels were significantly and directly correlated with all studied diabetic parameters which lead to conclude that MR-proADM can serve as prognostic indicator for GDM.