Background: The Australian criterion for diagnosing gestational diabetes mellitus (GDM) was changed in 2015 to mirror the internationally applied IADPSG criterion. Research has predicted this would increase the incidence of GDM due to the lower fasting threshold and a new 1-hour diagnostic value.
Aims: To quantify the impact of the IADPSG guideline on the incidence of GDM at a secondary hospital in Australia. It was hypothesised that the incidence would increase with no associated difference in maternal or foetal outcomes.
Materials and Methods: This secondary hospital only cares for women with diet controlled GDM, with those requiring insulin or BMI ≥45kg/m2 being referred to a tertiary hospital. The IADPSG criterion was introduced locally in September 2015. All births between January and June in 2015 (n=899) and 2016 (n=925) were included in the study. There were 71 women with GDM in 2015 and 56 in 2016. Blood glucose results and several pregnancy outcome data were analysed.
Results: Following the introduction of the IADPSG criteria, the incidence of GDM decreased from 7.90% to 6.05%. This 23% reduction was not statistically significant. There was no significant difference in maternal or foetal outcomes between the two cohorts. However, receiving tertiary hospital had a significantly higher (23%) incidence of GDM (p<0.01) in the 2017 period, under the new guideline. This is one of the highest recorded incidences in literature so far.
Conclusion: In a secondary hospital, the IADPSG criterion did not increase the incidence of GDM as expected but the incidence was markedly higher at the receiving tertiary hospital. More data is required to quantify the effect of the IADPSG criterion in Australia.