Study aim: To compare neonatal outcomes following metformin-first versus insulin treatment of maternal gestational diabetes mellitus in a randomized controlled trial Design: Single center prospective open -label parallel group superiority RCT Settings and conduct: Maternal Fetal Medicine Department of Obstetrics and Gynaecology Lady Reading Hospital MTI Peshawar Participants/Inclusion and exclusion criteria: Women aged ≥18 years with a singleton viable pregnancy randomized at 24+0–33+6 weeks with GDM inadequately controlled after 7–14 days of lifestyle intervention and glucose monitoring, and providing written informed consent for neonatal assessment and follow-up Pre-existing or overt diabetes HbA1c ≥6.5%urgent insulin requirement ketosis symptomatic hyperglycemia or fasting glucose 6.0–6.9 mmol/L with significant fetal overgrowth polyhydramnios current glucose lowering medication multiple pregnancy major fetal anomaly or growth restriction hypertension or preeclampsia imminent delivery significant hepatic renal disease acute kidney injury acidosis severe infection dehydration or relevant drug allergy inability to consent or complete follow-up or participation in another interventional trial Intervention groups: Metformin first treatment titared to tolerance and glucose response with prompt supplemental insulin Main outcome variables: Neonatal hypoglycemia blood glucose below the prespecified threshold within 48 hours of birth Birth weight large forgestationalage macrosomia respiratory distress NICU admission preterm birth low birth weight Apgar scores 1 and 5 minutesand neonatal death Percentage of fasting and 1hour postprandial glucose readings within targets maternal weight change insulin rescue and dose mode of delivery pre-eclampsia and adverse effects