Backgroup: Pregnancy is a diabeto-genic condition, which is why pregnancy with diabetes is one of the common medical and endocrinological disorder encountered in obstetrics. Diabetes Mellitus complications during pregnancy has become more common worldwide. About 0-4% of all pregnancies are complicated by diabetes mellitus and 90% of those are GDM. Aim of the study: This study was conducted to find out the maternal and fetal outcome of the pregnancies complicated by pre-gestational and gestational diabetes mellitus. Material & methods: This was a cross-sectional analytical study which was conducted in the Department of Obstetrics and Gynecology Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka. In this study, a total of 225 patients were selected using purposive sampling technique. There were three groups of pre-gestational diabetic, gestational diabetic and non-diabetic control, designated as Group A, Group B, Group C accordingly; and each consists of 75 patients. Duration of data collection was one year (July 2016 to June 2017). Information collected from all pregnant women (After 28 weeks of gestation) using a questionnaire made for recoding all relevant parameters under study, after proper counseling and taking written consent of the patient or her legal guardian. Results: History of GDM was significantly more common among patients with pre-GDM (38%) and GDM (18%) compared to controls. History of abortion, IUFD and congenital anomaly were significantly higher among pre-GDM mothers than GDM mothers and controls (p<0.05). History of deliveries with macrosomia and still birth was distributed similarly across the groups (p>0.05). Pre–GDM and GDM patients had significantly higher number of patients with HbA1C >6.5% than controls. Mean FBS and PPBS was significantly higher in pre-GDM & GDM patients than control (p<0.05). APGAR score was <7 in significantly higher number of pre–GDM and GDM babies than controls (p <0.05). Mean Weight of the babies was significantly lower among pre–GDM patients than GDM patients (p <0.05). Among pre–GDM patients and GDM patient’s cases of birth asphyxia, Hypoglycemia, hyperbilirubinemia and congenital anomalies were significantly higher than controls (p< 0.05). Conclusion: Interventions such as preconception care for women with pre-gestational diabetes, screening for early diagnosis, patient education, multidisciplinary approach and good metabolic control maintained throughout the pregnancy is the key to successful fetomaternal outcome.