Abstract
A random blood glucose concentration was determined in 2403 pregnant women attending an antenatal clinic at between 28 and 32 weeks' gestation. The calculated 99% cut off values were 6.1 mmol/l (110 mg/100 ml) within two hours after a meal and 5.6 mmol/l (101 mg/100 ml) more than two hours after a meal. Patients with a blood glucose concentration in excess of these values were referred for a 75 g oral glucose tolerance test. Of 59 referred, four were found to have previously unsuspected but unequivocal diabetes mellitus and another four to have impaired glucose tolerance on the basis of the World Health Organisation's criteria. Screening all antenatal patients by randomly measuring blood glucose concentrations is not only cheap and efficient but also does not interfere with the routine of busy antenatal clinics.