Random blood glucose sampling as an early antenatal screening test for diabetes mellitus

Random blood glucose was measured on 1,992 pregnant women during the initial attendance at our antenatal clinic. The visit usually took place during the first part of the second trimester. Women with a random blood glucose concentration in excess of 6.1 mmol/l within 2 hours of the last meal and 5.6 mmol/l more than 2 hours after the last meal were referred for a fasting blood glucose measurement. A 75 g oral glucose tolerance test was performed in those cases where the fasting blood glucose exceeded 4.0 mmol/l. The cut-off levels were exceeded in 22 cases, but only one of these women was found to be suffering from previously unsuspected diabetes mellitus, based on the criteria of WHO (1). Five other cases of gestational diabetes were not detected by the random blood glucose method. It is concluded that random blood glucose measurements cannot be recommended as a safe and reliable screening procedure during the early part of the second trimester.