Abstract:Introduction: GDM (gestational diabetes mellitus) is a common complication of pregnancy, and prevalence has become alarming. Insulin remains the cornerstone in management of diabetes mellitus but oral agents have been increasingly viewed as potential alternatives to insulin because it's economically low in cost, easier to administer and affordable to monitor compare to insulin. Aim: This study aimed to determine the effects of Gliclazide on the heart cytoarchitectonic and some biochemical indices of pregnant STZ (streptozotocin)-induced diabetic rats compare with insulin. Methods: Twenty (20) pregnant Sprague Dawley rats weighing between 130 g and 150 g were used for the experiments. The rats were divided into four (4) groups: Group 1 (Non-diabetic), Group 2 (Diabetic), Group 3 (Diabetic + Gliclazide) and Group 4 (Diabetic + Insulin). The glucose levels and body weights were monitoring daily. The experimental rats were sacrificed on the 19th on gestational period, blood samples and organs were collected for biochemical and histo-morphological examinations. Results: Gliclazide group rats showed significant increase in body weight compared with diabetic group (p ≤ 0.05). The blood glucose level of rats in gliclazide group was significantly reduced compared with other groups. There was significant increase in reduced GSH (glutathione) of gliclazide and insulin groups compared with diabetic group. MDA (malondialdehyde) and CAT (catalase) levels activities were significantly increase in diabetic group compared with other groups. Hormonal profiles and hematological parameters are significantly increased in gliclazide, and insulin group compared with diabetic group. There were distortions in the structural organization of heart of diabetic group while gliclazide and insulin groups showed remarkable improvements of the degenerative changes of the myocardium. Conclusions: Gliclazide glycemic control has shown beneficial effects on the cardiomyocytes damage in STZ-induced diabetic rats by maintaining the histological integrity of the heart leading to reduced degenerative changes in the myocardium.