Minimising COVID-19 risk is important, but so is testing for gestational diabetes

A Western Sydney University expert has warned that strategies designed to lower the risk of COVID-19 may lead more pregnant women and infants to suffer from the effects of undiagnosed and untreated gestational diabetes.

 

Professor David Simmons, from the University’s School of Medicine, is a global leader in diabetes research and the Chief Investigator of the world’s largest trial which is exploring how to treat gestational diabetes in early pregnancy.

 

In the Australian and New Zealand Journal of Obstetrics and Gynaecology (ANZJOG), Professor Simmons and colleagues from a range of Sydney hospitals raised concerns about the reduced diagnosis rates of Gestational Diabetes Mellitus (GDM) as a result of the global pandemic.

 

“The gold standard for detecting GDM that develops later in pregnancy is a two-hour oral glucose tolerance test (OGTT), which needs to be administered between 24–28 weeks’ gestation,” said Professor Simmons.

 

“The full OGTT requires women to attend testing centres for up to 2.5 hours, and submit to three blood tests. There have been concerns that such lengthy visits to pathology centres may place women at more risk of contracting COVID-19 – so there has been a shift toward less extensive testing.”

 

During the pandemic, women are often only being offered a fasting plasma glucose (FPG) test, which only requires a single blood test and takes only 15 minutes – however Professor Simmons said the FPG is not sufficient.

 

“The FPG may significantly reduce the time that women spend in clinics – and therefore decrease their chances of contracting COVID-19 in clinical settings – but the effectiveness of the test is also significantly impacted,” said Professor Simmons.

 

“In circumstances where the full OGTT is not possible, a better “one stop shop” compromise would be a partial OGTT – however women are not currently being offered this option.”

 

The ANZJOG article provides a comparison of the sensitivity and the likely effectiveness of the full OGTT test, compared with a one-hour, partial OGTT, and the 15-minute FPG:

 

Type of test

Sensitivity of test

Duration of test

Blood samples collected

% of cases likely to be missed

Full OGTT

100%

2–2.5 hours

3

N/A

Partial OGTT

88–91%

1 hour

2

12%

FPG

38–64%

15 minutes

1

40–50%

 

Professor Simmons said the FPG is likely to miss more than 40 per cent of cases of gestational diabetes – which is a serious concern.

 

“Undiagnosed and untreated gestational diabetes can lead to a range of adverse health impacts for mother and infant, including increased pre-eclampsia, shoulder dystocia, birth trauma and postnatal depression. At the most extreme, the condition can lead to stillbirth,” he said.

 

As the COVID-19 pandemic continues to impact society, Professor Simmons says a balance needs to be sought between reducing the exposure of pregnant women and still enabling effective screening for diabetes in pregnancy.

 

“Where pathology centres can allow sufficient social distancing, the OGTT remains the gold standard for diagnosis throughout pregnancy and should still be offered to all women,” he said.

 

“If social distancing requirements cannot be observed, alternatives should continue to be offered. The one hour OGTT is the best compromise, as its shorter than the two-hour test and is still Medicare billable. Another viable option would be for women to wait outside the testing centre, perhaps in their car, in between blood collections during the 2 hour OGTT.”

 

Irrespective of the options available, Professor Simmons said the best approach would be for the inherent risks to be explained to women, and allow them to make informed decisions based on their own health circumstances.

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