key: cord-0812501-pbp8sv40
authors: van Gemert, Tegan E.; Moses, Robert G.; Pape, Alexia V.; Morris, Gary J.
title: Gestational diabetes mellitus testing in the COVID‐19 pandemic: The problems with simplifying the diagnostic process
date: 2020-07-13
journal: Aust N Z J Obstet Gynaecol
DOI: 10.1111/ajo.13203
sha: 0fea1f0f9b78bbe64817381149911210a302345c
doc_id: 812501
cord_uid: pbp8sv40

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.

Gestational diabetes mellitus (GDM) is a very common medical problem found in pregnancy. The Australasian Diabetes in Pregnancy Society (ADIPS) 1 recommends that all women in every pregnancy be tested, ideally using a two-hour glucose tolerance test (GTT). The diagnostic criteria come from recommendations of the World Health Organization (WHO) which were based on the results of the Hyperglycaemia and Pregnancy Outcomes study (HAPO). 2 In Australia, in a nationally representative population, the prevalence of hyperglycaemia in pregnancy (HIP) was found to be 13.1% with 0.4% having diabetes in pregnancy (DIP) and 12.7% having GDM. 3 Testing in centres or regions with a higher number of women with risk factors is likely to show a higher prevalence.

While so far with the COVID-19 pandemic there appear to be no concerns with the outcome of pregnancies, 4 it would be potentially prudent to reduce the number of women requiring a GTT in order to reduce person-to-person contact and limit the time spent in a health service environment. While the WHO has not made any recommendations about simplifying the diagnostic process, 5 multiple professional bodies, including those from Australia, 6 Canada, 7 and the United Kingdom, 8 It is inevitable that not proceeding to a GTT for women with a fasting glucose ≤4.6 mmol/L will underdiagnose GDM. The purpose of the study herein reported is to examine the extent of this underdiagnosis.

This study was conducted in the Illawarra area centred around the city of Wollongong. The area is very suitable for epidemio- 

This audit conforms to the standards established by the National Health and Medical Research Council for ethical quality. The

District Health and Medical Human Research Ethics Committee did not require the audit herein reported to be reviewed. 12

In total 16 552 results for the 75 g oral GTT during pregnancy were identified over this six-year period. There were 289 records (1.7%) with some missing data and these were not considered further. Of the remaining 16 263 results, HIP was diagnosed in 2031 (12.5%) women of whom 39 (0.2%) had DIP and were not considered further. There were 1992 women with GDM (12.2%) and these were considered in further analyses.

Percentages of gestational diabetes mellitus (GDM) positive cases that would be missed for different fasting glucose cutoffs if each cut-off was used to determine no need for a glucose tolerance test (95% confidence intervals). Of women diagnosed with GDM, 376 (18.9%) were at <20 weeks gestation and 1616 (81.1%) were diagnosed at ≥20 weeks gestation. Most women diagnosed with GDM were aged more than 30 years (85.2%).

Of the 1992 women diagnosed with GDM, 596 (29%; 95% CI 28.0-32.0%) had a fasting glucose of ≤4.6 mmol/L and would have been missed. The percentage of cases of GDM missed for different fasting glucose levels from 3.5 to 5.0 mmol/L with 95% CI are shown in Figure 1 . As an example, based on these data, the cut-off for the fasting glucose required to pick up at least 95% of GDM cases would be ≥4.0 mmol/L.

The temporary COVID-19 pandemic revised guidelines for the diagnostic pathway of pregnant women being tested for GDM will certainly reduce the number of women being potentially exposed but will miss about a third of all cases. Perhaps women with a low fasting level but diagnostic one and/or two-hour levels may be in a lower risk group for adverse pregnancy outcomes but there is limited data available on this. In 2019 McIntyre et al. 13 presented data from five of the HAPO sites and found that 25% of women with a fasting glucose <4.6 mmol/L had GDM but their outcomes were similar to women who were not diagnosed with GDM. The ethnicity of the women at these HAPO sites was not detailed and may not necessarily be relevant to an Australia population. 

ADIPS Consensus Guidelines for the Testing and Diagnosis of Hyperglycaemia in Pregnancy in Australia and New Zealand

Hyperglycemia and adverse pregnancy outcomes

The prevalence of hyperglycaemia in pregnancy in Australia

Global interim guidance on coronavirus disease 2019 (COVID-19) during pregnancy and puerperium from FIGO and allied partners: information for healthcare professionals

COVID -19GDM Diagn osis0 30420 ADIPS ADSAD EADAf orWeb site.pdf 7. Urgent update -temporary alternative screening strategy for gestational diabetes screening during the COVID-19 pandemic. A joint consensus statement from the Diabetes Canada Clinical Practice Guidelines Steering Committee and the Society of Obstetricians and Gynaecologists of Canada

Queensland Clinical Guidelines. Gestational Diabetes Mellitus. Notice of Update During COVID-19 Pandemic

Census Community Profiles -Illawarra Code 107 (SA4)

Using fasting plasma glucose to identify women with gestational diabetes at low risk of complications