Abstract Objective: To compare the fetomaternal outcomes in terms of congenital anomalies, miscarriage, macro-somia, polyhydraminos, preterm labor, IUGR, still birth, early neonatal death and operative delivery bet-ween known diabetic and gestational diabetic patients (GDM). The effect of glycemic control on these com-plications was also studied. Methods: It was a two year comparative analytic study done at Gynae unit III, SIMS, Services Hospital Lahore from Jan 2013 to Dec 2014. Patients were divi-ded into two groups, patients with pre-existing type1 or 2 diabetes and those having GDM. Results: A total of 124 patients were found to be dia-betic over 2 year study period, out of which 61.3% had gestational diabetes. Family history of diabetes was present in 58% of GDM patients and 42% of known diabetic patients (P > 0.05). 52.6% of GDM patients Wasim T. 1 Professor of Obstetrics & Gynaecology SIMS / Services Hospital, Lahore Amer W. 2 Professor of Medicine LMDC, Ghurki Trust Hospital, Lahore Majrooh A. 3 Professor of Community Medicine SIMS / Services Hospital, Lahore had no complication and delivered uneventfully (p < 0.05). Macrosomia was most frequent complication (26.3%) of GDM group and 29% of known diabetic patients. No congenital anomaly and miscarriage occu-rred in GDM group (P < 0.05). Operative delivery was high 44% in known diabetic patients as compared to 33% of GDM patients but not statistically significant. Perinatal outcome was comparable in both groups. Optimum glycemic control (HbA 1 c ≤ 6%) was signi-ficantly associated with fewer complications p = 0.001. Conclusion: GDM is an increasing health problem and has been associated with fetomaternal complicat-ions. Screening is recommended for general pregnant population. Early diagnosis, patient education, proper follow up in close liaison with physician results in bet-ter glycemic control and improved maternal and peri-natal outcome in diabetic pregnant patients.