Gestational diabetes mellitus testing in the COVID-19 pandemic: The problems with simplifying the diagnostic process.

BACKGROUND: Multiple professional bodies have temporarily revised recommendations for gestational diabetes mellitus (GDM) testing during the COVID-19 pandemic to reduce person-to-person contact. The current Australian temporary criteria advise that if the fasting glucose is ≤4.6 mmol/L, then no glucose tolerance test (GTT) is required. AIMS: The aim of this study is to examine the extent of underdiagnosis of GDM using a fasting glucose ≤4.6 mmol/L as a cut-off to determine that a GTT is not necessary. MATERIALS AND METHODS: De-identified data from pregnant women having a GTT test in the Illawarra area during a six-year period was used to determine the number of women with GDM and the proportion of positive cases that would be missed for different fasting glucose values. RESULTS: There were 16 522 results identified and GDM was diagnosed in 12.2%. The majority of women were more than 30 years of age (85.2%) and diagnosed at ≥20 weeks gestation (81.1%). Of those diagnosed with GDM, 29% had a fasting glucose of ≤4.6 mmol/L and would have been missed. CONCLUSIONS: Our results show that using a fasting glucose of 4.6 mmol/L or less would miss nearly a third of women who would otherwise be diagnosed with GDM.

Fasting target for hyperglycaemia in pregnancy.

Knowledge of the fasting plasma glucose of healthy women may assist in the setting of treatment targets for women with hyperglycaemia in pregnancy (HIP). This study examines the pregnancy glucose tolerance test results of 3344 women without HIP collected over a three-year period. The median fasting plasma glucose was 4.4 mmol/L with an interquartile range of 4.2-4.6 mmol/L and a 5th to 95th centile of 3.8-4.9 mmol/L. As the diagnostic fasting glucose level for HIP is ≥5.1 mmol/L, these data support a treatment target of ≤5.0 mmol/L.

Seasonal Changes in the Prevalence of Gestational Diabetes Mellitus.

OBJECTIVE: To determine the effect of different seasons on the prevalence of gestational diabetes mellitus (GDM) by using World Health Organization criteria. RESEARCH DESIGN AND METHODS: The results of all pregnancy glucose tolerance tests (GTTs) were prospectively collected over a 3-year period in a temperate climate, and the results were grouped by season. RESULTS: The results of 7,369 pregnancy GTTs were available for consideration. In winter, the median 1-h and 2-h glucose results after GTT were significantly (P < 0.0001) lower than the overall 1-h and 2-h results. The prevalence of GDM at the 1-h diagnostic level was 29% higher in summer and 27% lower in winter than the overall prevalence (P = 0.02). The prevalence of GDM at the 2-h diagnostic level was 28% higher in summer and 31% lower in winter than the overall prevalence (P = 0.01). CONCLUSIONS: The prevalence of GDM varies according to seasons, which leads to the possible overdiagnosis of GDM in summer and/or underdiagnosis in winter. Further research into standardization of the GTT or seasonal adjustment of the results may need to be considered.

The prevalence of hyperglycaemia in pregnancy in Australia.

BACKGROUND: The Australasian Diabetes in Pregnancy Society (ADIPS) has recently endorsed the World Health Organization (WHO) terminology and classification of hyperglycaemia in pregnancy. The prevalence is likely to increase, but no prospective data are available for a representative Australian population. AIMS: To determine the prevalence of hyperglycaemia in pregnancy (HIP) using results from both the public and private sectors in a population that has a similar ethnicity to the overall Australian population. MATERIAL AND METHODS: The results of all pregnancy oral glucose tolerance tests (POGTT) in the public sector and by a dominant private pathology provider in a major city have been prospectively collected for a three-year period and analysed using the ADIPS (WHO) criteria. RESULTS: The prevalence of hyperglycaemia in pregnancy (HIP) was 13.1% with diabetes mellitus in pregnancy (DIP) being 0.4% and gestational diabetes mellitus (GDM) being 12.7%. CONCLUSION: The new criteria will diagnose about one-third more women with GDM than the previous ADIPS criteria. This will have resource and health implications. Focussed local health economic data will be important.

The impact of potential new diagnostic criteria on the prevalence of gestational diabetes mellitus in Australia.

OBJECTIVE: The International Association of Diabetes and Pregnancy Study Groups (IADPSG) has proposed new criteria for the diagnosis of gestational diabetes mellitus (GDM). The aim of this study was to compare the prevalence of GDM when IADPSG criteria were used with the prevalence when the current Australasian Diabetes in Pregnancy Society (ADIPS) criteria were used. DESIGN, SETTING AND PARTICIPANTS: This was a prospective study over a 6-month period, examining the results of all glucose tolerance tests (GTTs) conducted for the diagnosis of GDM in Wollongong, a city using the public and private sectors. MAIN OUTCOME MEASURES: The prevalence of GDM using the existing (ADIPS) and the proposed (IADPSG) criteria. RESULTS: There were 1275 evaluable GTTs (571 public and 704 private). Using the current ADIPS diagnostic criteria, the prevalence of GDM was 8.6% (public), 10.5% (private) and 9.6% (overall). Using the proposed IADPSG criteria, the prevalence of GDM was 9.1% (public), 16.2% (private) and 13.0% (overall). CONCLUSIONS: The proposed IADPSG criteria would increase the prevalence of GDM from 9.6% to 13.0% (P < 0.001). In our study in the Wollongong area, which has a population with a predominantly white background, this increase came mainly from older women attending a private pathology provider. Data from both the public and private sectors need to be included in any discussion on the change in prevalence of GDM.