Abstract: A hospital based case-control study was conducted with 112 gestational diabetes mellitus diagnosised during six years between 1998 and 1993 to explore the risk fackors of GDM and to determine perinatal and maternal outcomes. Univariate analysis showed the follwing significant risk fackors were a family history of diabetes, spontaneous abortion, poor obstetric history, the presence of hypertension, obesity and parity. Conditional Logistic confirmed the effects of obesity and a family history of diabetes and parity.