Objectives: Teenage pregnancy with gestational diabetes mellitus (GDM) offers a real challenge to the health system and needs a special care. We aimed to evaluate possible obstetrical and neonatal adverse events of different treatment protocols in adolescent GDM including lifestyle, metformin (MTF), and insulin. Methods: All teen pregnant women ≤ 19 years old visiting Baghdad Teaching Hospital throughout four years (from June 1, 2016 till May 31, 2020) diagnosed with GDM were included in this cohort study and followed-up closely throughout pregnancy and after delivery. Included adolescents were put on lifestyle alone during the first week of presentation. Adolescents who reached target glucose measurements were categorized into lifestyle group, while other adolescents were randomly allocated into MTF and insulin groups. Also, adolescent pregnant women without GDM were recruited as control group using computer randomization. Results: The GDM (110 cases) and control (121 individuals) groups had matched general features at recruitment except for diabetes family history. Also, GDM treatment groups had matched features. Glycemic readings (fasting and random) was significantly (p< 0.05) higher in insulin group having odds ratio (OR) of 1.41, and 1.57, respectively. In MTF group, significant protective OR was found in preeclampsia (OR=0.76, p< 0.05). MTF showed non-significant protective OR regarding prematurity and five minutes Apgar score>7 [(OR=0.83, p=0.24), and (OR=0.94, p=0.73), respectively], and significant protective association with large for gestational age and admission to neonatal intensive unit. Insulin had significantly higher prematurity, small for gestational age, and hypoglycemia [OR=1.89, 2.53, and 2.84, respectively]. Conclusion: Metformin (MTF) showed less pregnancy and neonatal complications in adolescent GDM than insulin and lifestyle. doi: https://doi.org/10.12669/pjms.37.4.3966 How to cite this:Jasim SK, Al-Momen H, Wahbi MA. Treatment options of Adolescent Gestational Diabetes: Effect on Outcome. Pak J Med Sci. 2021;37(4):1139-1144.  doi: https://doi.org/10.12669/pjms.37.4.3966 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.