A glucose load screening test should be performed on every pregnant woman. At 24-28 weeks of gestation, a 50 g glucose screening test, i.e., at any time (without fasting), glucose less than 7.8 mmol/L (140 mg/dl) 1 hour after taking oral glucose, can exclude gestational diabetes. If the blood glucose is greater than or equal to 7.8 mmol/L (140 mg/dl) 1 hour after taking glucose, gestational diabetes is suspected and a further 100 g glucose tolerance test is required to make the diagnosis according to the O’Sullivan criteria. O’Sullivan criteria (venous plasma) Fasting – 5.9mmol/L (105mg/dl) 1 hour – 10.6mmol/L 190mg/dl 2 hours – 9.2mmol/L (165mg/dl) 3 hours – 8.1mmol/L (145mg/dl) Any of the above 4 glucose values Gestational diabetes is diagnosed when any two of the above blood glucose values meet or exceed the above criteria. Unless there is significant hyperglycemia with acute metabolic failure or obvious symptoms, the blood glucose should be retaken on another day to confirm that the diagnostic criteria are met. Fasting is defined as no energy intake for at least 8 hours. Blood glucose should be retested after a stressful condition (infection, trauma, surgery).