Type 2 diabetes (T2D) and hypertension are the commonest comorbidities in patients with SARS-CoV-2, and Bornstein et al (2020) draw attention to emerging evidence for a direct metabolic and endocrine link to the disease process.
Given this context, it is perhaps timely to reconsider gestational diabetes mellitus (GDM), defined as glucose intolerance that is first diagnosed in pregnancy; increases the risk of complications for both mother and baby during pregnancy; and has a European prevalence of 5.4%, ranging from 3.8%–7.8% (Eades et al, 2017).
Further, Van-de-l'Isle et al (2020) note that GDM complicates around one in 16 pregnancies in the UK, citing evidence that GDM treatment improves perinatal outcomes: women with untreated GDM have a four-fold risk of having a baby large for gestational age or macrosomia (birthweight >4 000 g) compared with those treated for GDM. Such observations strengthen the need for improved identification of GDM, and Van-de-l'Isle et al (2020) investigated the differences in detection rate for GDM between that recommended by the National Institute for Health and Clinical Excellence (NICE) and the testing considered appropriate during the COVID-19 pandemic by the Royal College of Obstetricians and Gynaecologists (RCOG). Following RCOG guidance, the overall rate of women identified with GDM fell from 7.7%–4.2%, and of 230 women who tested negative according to the RCOG criteria but who subsequently had an oral glucose tolerance test, 20.4% were diagnosed with GDM according to the NICE criteria. With RCOG COVID-19 GDM screening failing to detect 47 of 82 (57%) women subsequently identified as gestational diabetics, Van-de-l'Isle et al (2020) suggest that RCOG GDM screening ‘cannot be recommended for general use.’
With lockdown having confined many people to home, often for months on end, the findings of Wagnild et al (2019) assume greater significance today. Their pre-pandemic study of 188 pregnant women in the North East of England investigated the association between objectively measured sedentary time and self-reported television time during pregnancy with incident GDM and plasma glucose concentrations among women at high risk for GDM. Wagnild et al (2019) suggested that reducing total sedentary time and breaking up sedentary time might be a useful strategy for managing blood glucose concentrations among pregnant women at high risk of GDM, reporting that higher television time during the second trimester was associated with a greater incidence of GDM.
Although testing and the avoidance of prolonged periods of sitting down are important aspects of addressing GDM, a pivotal aspect is the role of nutrition, and in recent years the concept of T2D no longer being a reversible condition has gained traction, with low-carbohydrate diets coming under increased study. For example, Hallberg et al (2019) present a narrative review of the evidence for T2D reversal, pointing out that before the discovery of insulin in 1921, low-carbohydrate diets were routinely prescribed as an effective treatment. And the first sentence of a report by the Parliament of Western Australia (2019) states: ‘If there is one thing to take away from this report, it is that T2D can go into remission and it need not be a lifelong progressive chronic illness.’
Might a low-carbohydrate approach to GDM be feasible? The Parliament of Western Australia (2019) thinks so, noting that the Czech Republic has amended its guidelines to recognise the benefit of low carbohydrate intake for women with GDM, and lowering the recommendation for 250 g of carbohydrates split into six portions, to less than 200 g per day. Addressing concerns over carbohydrate intake at this level risking gestational ketosis, thought to pose risks to the offspring, the report authors state that the Czech Republic guidelines were amended in 2016 in response to growing evidence that diets with low glycaemic load delivered better results: ‘Now, fewer than 10% of women require medication. Gestational diabetes specialist Dr Hana Krejcí notes that carbohydrate intake is individual, and many women can achieve good glycaemic control after eliminating free sugars and foods with a high glycaemic index.’
With the COVID-19 pandemic generating growing interest in metabolic aspects of the disease, combined with mounting evidence that a low-carbohydrate approach to GDM management is worthy of further research, it appears possible that GDM may evolve with time to have a lower prevalence than that cited by Eades et al (2017).