Maternal DM is usually associated with structural and functional changes in the fetal heart. Fetal echocardiography plays a key role in the identification of these changes. The aim of this paper assesses the importance of fetal echocardiography in the detection of structural and functional diseases of the heart in diabetic pregnant mothers' fetuses and compare them with uncomplicated pregnancy. We enrolled 100 pregnant mothers with age between 18 and 45 years and the age of mean is about 27.68 ± 3.11,50 diabetic pregnant women and 50 non- diabetic pregnant women; the diabetic group subdivided into; pre-GDM: 15 patients & GDM: 35 patients. Fetal echocardiography was done for all cases. We evaluate RV & LV dimensions and function by conventional M mode, 2D and Doppler imaging. Our study shows significant difference in comparing cases with control group as regards PWDd, PWDs, but highly statistically significant difference as regard IVSd, IVSs, EF%, Left atrial diameter, Aortic to LA diameter ratio, RV diameter and Stroke volume (SV).This means higher risk if LVH (HCM) in fetuses of diabetic mothers, While there was no difference significantly between them as regard LVESD, LVEDD, Aortic diameter, RV/LVED. Also, it shows a statistically significant difference between Pregestational and gestaional group regarding LVESD, RV, TVEV, TVAV and TV max V, AV max V, PV mean V dimensions and highly statistically significant difference regarding LVEDD, TV maxV, in contrast, there was no difference among the studies groups as regard IVSd, IVSs, PWDd, PWDs, AO, LA, LA/AO, RV/L ED ratio, EF (%), MVEV, MVAV, MV E/A ratio, MV max V, MV mean V, TV E/A ratio, TV mean V, AV mean V, PV max v 0.05. A higher incidence of congenital structural as well as functional abnormalities in fetal hearts is seen within fetuses of diabetic pregnant mothers. Fetal echocardiography is a sensitive parameter in the detection of these abnormalities.