The clinical impact of screening for gestational diabetes

Abstract

Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance during pregnancy. In Denmark the health service offers selective screening for GDM, i.e., admission to an oral glucose tolerance test (OGTT) after pre-screening with interview for clinical risk factors for GDM, two capillary fasting blood glucose (cFBG) measurements and a urine test for glucosuria. The aim of the present study was to investigate the power of the pre-screening to identify GDM and the screening to predict adverse clinical outcome. A retrospective investigation of pregnant women undergoing screening during 1998 at Vejle County Hospital, Denmark was undertaken. The two most frequent pre-screening criteria for OGTT were body-mass index (BMI) > or = 27 kg/m2 and age > or = 35 years. The highest odds ratio (OR) of 9.07 (95% CI: 2.60 to 63.70) for GDM had glucosuria and the lowest (zero) had cFBG. The frequency of complicated delivery was similar in GDM (58%) compared to non-GDM (56%). The best predictor of complicated delivery was a BMI with OR = 1.50 (95% CI: 0.87 to 2.60) for BMI > or = 27 kg/m2 vs. < 27 kg/m2. The best predictor of adverse neonatal outcome was a capillary blood glucose 120 min after glucose load (cBG(120 min)) > or = 9.0 mmol/l (OR = 3.18, 95% CI: 1.14 to 8.89). The intermediary endpoint GDM was not superior for predicting adverse maternal and neonatal outcome. The cumulative probability distribution of cBG(120 min) after a 75 g glucose load was not homogeneously distributed in groups stratified according to maternal and foetal outcome. A changed slope was seen after cBG(120 min) 9.0 mmol/l. Screening cFBG of 4.1 mmol/l was unable to predict GDM and adverse outcome. Glucosuria was too rare to be effective as a screening tool. Pre-screening did not identify GDM. The best predictor of complicated delivery was a high BMI. The best predictor of foetal adverse outcome was cBG120 miin > or = 9.0 mmol/l after a 75 g glucose load. Identical fraction complications were present in GDM and non-GDM. A refinement of the screening procedure is highly needed, and this has been initiated in Denmark.