Dissertation (MMED Obstetrics and Gynaecology)Background: Gestational Diabetes Mellitus (GDM) is a complication of pregnancy characterized by the increase of insulin resistance leading to maternal Hyperglycaemia and alteration of newborn blood glucose. Alteration of cord blood glucose level can be used to predict maternal glycemic state. A newborn cord blood glucose level is a characteristic of pregnancy complicated by Gestational diabetes mellitus. The prevalence of GDM globally ranges from 6-13% with 5-9% in sub-Saharan Africa while is Tanzania has 19.5% GDM prevalence. Objective: The study aimed at determine utility of cord blood glucose of a new born as a predictor of maternal gestational diabetes mellitus. Methods: This was a cross sectional study design in quantitative approach of which a structured questionnaire and systematic sampling technique was used for data collection, of which blood sample were taken from umbilical vein of a newborn. New born with Hyperglycaemia or hypoglycemia, their mothers, blood glucose of was taken. For women with Hyperglycaemia, OGTT was done; after two hours to confirm the diagnosis of GDM.SPSS version 20 software program was used for data entry and analysis. Results: 252 newborn were enrolled and regarding cord blood glucose of the newborns, 153 (60.70%) were Hyperglycemic, compared to 99 (39.30%) of newborns who were hypoglycemic. Concerning birth weight majority had less than 4kg, 183 (72.62%) and 69 (27.38%) had more than 4kg.The prevalence of GDM among women delivered at DRRH was 29.4%. Conclusion: The prevalence of GDM in women delivered at DRRH is high in the study area. There is a positive association between cord blood glucose of a new born versus GDM. Mothers whose newborns were Hyperglycemic were two times at risk of having GDM compared to mothers whose newborns had hypoglycemia. Therefore, there is a need of a close attention for high risk mothers to be screened in order to reduce the magnitude and the disease’s burden.