The impact of adoption of the International Association of Diabetes in Pregnancy Study Group criteria for the screening and diagnosis of gestational diabetes

Abstract

The objective of the study was to compare the International Association of Diabetes in Pregnancy Study Group (IADPSG) and the Canadian Diabetes Association (CDA) criteria for the diagnosis of gestational diabetes mellitus (GDM). This was a retrospective cohort study involving all pregnant women who underwent screening for GDM at a tertiary medical center between 2008 and 2011. Diagnosis of GDM during the study period was based on the CDA 2008 recommendations of universal screening with a 50 g oral glucose challenge test (GCT; threshold 140 mg/dL [7.8 mmol/L]) and a diagnostic test using a fasting 2 hour, 75 g oral glucose tolerance test (OGTT). Diagnosis of GDM required the presence of 2 or more abnormal values, whereas a single abnormal value was diagnostic of impaired glucose intolerance. Because the OGTT thresholds based on the IADPSG criteria are lower than the CDA 2008 thresholds (92 mg/dL [5.1 mmol], 180 mg/dL [10.0 mmol/L], and 153 mg/dL [8.5 mmol/L]), we identified a group of women who would have been diagnosed as GDM based on the IADPSG criteria but not the CDA 2008 criteria (OGTT-IADPSG group). The pregnancy outcome of that group as well as that of women with a positive OGTT according to the CDA 2008 criteria (OGTT-CDA group) and women with a negative OGTT (OGTT-NEGATIVE group) was compared with that of a control group consisting of women with a negative GCT (GCT-NEGATIVE group). Overall, 5429 women were eligible for the study, of which 4183 were included in the GCT-NEGATIVE group, 526 in the OGTT-NEGATIVE group, 155 in the OGTT-IADPSG group, and 385 in the OGTT-CDA group. Applying the IADPSG criteria to the study population would increase the rate of GDM from 3.2% (7.3% when including impaired glucose intolerance) to 10.3%. The majority of the increase in the rate of GDM was attributed to the use of a single abnormal value to define GDM (5.3% increase) rather than the use of lower threshold values (1.8% increase). Of the 3 threshold values, the lower 1 hour threshold was the most significant contributor to the higher GDM rate. A positive OGTT in both the OGTT-IADPSG group and the OGTT-CDA group was independently associated with a higher rate of the composite adverse outcome (odds ratio, 1.4; 95% confidence interval, 1.1-1.9). The use of the IADPSG criteria instead of the CDA criteria would result in a considerable increase in the rate of GDM, but this also appears to identify additional women at similar risk of adverse pregnancy outcome. Further studies are needed to determine whether this observation persists after controlling for confounders such as body mass index as well as whether treatment in these cases would improve perinatal outcome.