BACKGROUND

The prevalence of gestational diabetes (GDM) is rising and affects 1 in 20 pregnancies in Australia¹ . The proposed new diagnostic criteria, based on the Hyperglycaemia and Pregnancy Outcome (HAPO) study² , are expected to further increase this number.

OBJECTIVE

To compare the number of women diagnosed with GDM when applying the current (FBG ≥5.5, 2hr ≥  8.0mmol/L) and proposed new IADPSG diagnostic criteria  (FBG ≥  5.1, 1hr  ≥  10  and 2hr ≥ 10mmol/L).   

RESEARCH DESIGN AND METHODS

All women attending Southern Health for antenatal care are screened for GDM at 26 to 28 weeks gestation. [75g Glucose Challenge Test (GCT) with 75g Oral Glucose Tolerance Test (OGTT) if GCT positive, or OGTT only if considered high risk]. The number of women with GDM was retrospectively classified according to current and new diagnostic criteria over the 6 months between July and December 2011.

RESULTS

3663 deliveries occurred during the study period and 655 women (18%) underwent an OGTT. The prevalence of GDM according to the old versus new criteria was 20 and 26% respectively. The number of women diagnosed at each time point is listed in Table 1. Almost seven percent (44/655) of women would be diagnosed only on the new proposed 1 hour level.

Table 1: Rates of GDM By Each Glucose Measure

CONCLUSION

When the current diagnostic paradigm for GDM at Southern Health is compared to the proposed IADPSG criteria, there is approximately a 5% increase in the rate of diagnosis of GDM. Much of this increase will be due to a doubling in women who will satisfy the lower fasting glucose threshold of ≥  5.1mmol/L. It is anticipated that this, combined with the recommendation that all women be offered an OGTT in pregnancy, will significantly increase demand on diabetes in pregnancy services.

Acknowledgements: We would like to thank the Pathology department at Southern Health for allowing us access to the data.