Random capillary blood glucose and conventional selection criteria for glucose tolerance testing during pregnancy

The normal variation of random capillary blood glucose values and the usefulness of elevated (greater than or equal to 6.5 mmol/l) blood glucose values as a selection criterion for oral glucose tolerance testing (OGTT) during pregnancy were investigated. A consecutive series of 1,500 pregnant women without signs or symptoms of diabetes and 81 pregnant women with conventional selection criteria for OGTT were studied. The mean blood glucose value was 4.66 mmol/l and the 95% tolerance interval of all blood glucose values was 2.93-6.38 mmol/l. Blood glucose levels were not influenced by time of day or trimester of pregnancy. A blood glucose value of 6.5 mmol/l or higher was found in 174 women, 10 of whom had an abnormal OGTT. Four of thirty women with glycosuria or signs of accelerated fetal growth and 7 of 81 women with conventional selection criteria had abnormal OGTT's. The incidence of carbohydrate intolerance during pregnancy was 1.3%. The results of this study suggest that an elevated (greater than or equal to 6.5 mmol/l) random capillary blood glucose value may be a good selection criterion for OGTT in addition to conventional selection criteria when screening for carbohydrate intolerance during pregnancy.