Gestational diabetes mellitus screening in pandemic times: Are there viable alternatives?

The COVID‐19 outbreak has changed medical care guidelines across all medical specialties. Various patients are in vulnerable situations where postponing care is not an option, such as the case for pregnant women. Efforts are being made to maintain the quality of care during pregnancy while simultaneously reducing exposure to COVID‐19.

Recently, Canadian ¹ and UK ² Societies of Obstetrics and Gynaecologists alongside Queensland Health ³ proposed alternatives to the screening of gestational diabetes mellitus (GDM) during the COVID‐19 pandemic. In short, the alternative recommendation for GDM screening during pregnancy involves demographic characteristics combined with haemoglobin A1c (HbA1c) or non‐fasting random plasma glucose for all pregnant women without pre‐existing diabetes. However, while HbA1c above the 5.7% threshold is related to high specificity, it has low diagnostic sensitivity of approximately 25% as a GDM predictor. ¹

The ultrasound measurement of maternal visceral adipose tissue (m‐VAT) has been shown as a useful indicator of GDM among pregnant women, emerging as a marker of metabolic risk with greater accuracy than pre‐pregnancy body mass index (BMI) compatible with obesity that reaches maximum sensitivity ranging from 20% ⁴ to 56%. ⁵ m‐VAT can also be easily implemented during a routine ultrasound with no additional cost and fast learning curve among sonologists and sonographers. The probe is placed in a sagittal position 2 cm above the maternal umbilical scar and the electronic caliper placed from the aortic anterior wall to the linea alba. However, despite the aforementioned benefits, there is no established consensus regarding the cut‐off for this test. Different m‐VAT thresholds were found to be associated with increased GDM risk, ranging from 42.7 ⁴ to 48 mm, ⁶ when controlling for maternal age, pre‐pregnancy BMI and related to GDM diagnostic criteria proposed by the International Association of Diabetes and Pregnancy Study Groups (IADPSG). External validity of the findings is suggested by adjusting for ethnicity, maternal age and educational level confounders in previous regression analyses with similar results. ⁴ , ⁶ The m‐VAT sensitivity, a critical assessment of a diagnostic test, when using a 42.7 mm threshold resulted in an impressive performance of 87% (95% CI 60–98%), with a specificity of 62%. ⁴

Our group recently demonstrated that a 45 mm m‐VAT threshold for early pregnancy screening among a low‐risk outpatient pregnant sample showed significant crude and adjusted odds ratios of 13.4 (95% CI 2.9–61.1) and 8.9 (95% CI 1.9–42.2), respectively. ⁵ A similar result was obtained among pre‐gravid non‐obese women (BMI < 25.0), with crude and adjusted odds ratios of 16.6 (95% CI 1.9–142.6) and 14.4 (95% CI 1.7–125.7), respectively. In pre‐gravid obese women (BMI > 30), the use of a 45 mm m‐VAT threshold was not significantly able to predict GDM risk. The final accuracy of the 45 mm m‐VAT threshold showed a 66% ability to predict GDM in the whole sample. Not only so, but the predictive ability of the threshold increased to 72% among non‐obese pre‐gravid women only. ⁵

We believe that the inclusion of m‐VAT during routine early ultrasound can identify patients who would benefit from additional investigations regarding GDM, as well as identify patients who do not require unnecessary laboratory tests, which can risk exposure to COVID‐19. As this procedure can be done in the first 20 weeks of pregnancy, a nuchal translucency evaluation could be used as a form of risk stratification for GDM.