Aims: To highlight the variation in the diagnosis of gestational diabetes (GDM) as defined by six well-accepted international expert panels.
Methods: Two thousand, five hundred and fifty-four pregnant women underwent a 75-g oral glucose tolerance test for routine, antenatal GDM screening. They were classified using the criteria of the American Diabetes Association, Australasian Diabetes in Pregnancy Society, the Canadian Diabetes Association, the European Association for the Study of Diabetes, the New Zealand Society for the study of Diabetes and the World Health Organization (WHO).
Results: Between any two criteria, both the GDM prevalence (range; 7.9-24.9%) and the women classified differently [range; 70 (2.7%)-454 (17.8%) women], was significant (P<0.001). The most inclusive criteria, i.e. Australasian, despite generating the highest prevalence of GDM, did not pick up all the women identified by the most restrictive criteria, i.e. Canadian. The Australasian and the WHO criteria were associated with an increase in the number of Caesarean sections [odds ratio (OR); 1.64, 1.45, respectively] while the American, Canadian and New Zealand criteria identified an increase in macrosomia (birthweight>or=4000 g) incidence (OR; 2.09, 2.01, 1.92, respectively).
Conclusions: The guidelines of the various professional committees, being based on consensus and expert opinion, show major discrepancies in their ability to identify women with GDM and their capacity to predict adverse pregnancy outcome. Only evidence-based criteria derived from reliable and consistent scientific data will eliminate the confusion caused in clinical practice.