In reply: Taylor welcomes a strong evidence base for clinical practice, which is echoed by d’Emden and colleagues. However, their strong support for the current Australian diagnostic criteria for gestational diabetes mellitus (GDM) is surprising, given that these criteria are the product of an “Ad Hoc Working Party” report.1 This guideline, published in 1991, clearly acknowledged a lack of strong evidence and advocated criteria that were based on best available rounded values for the 95th centile of venous plasma glucose (VPG) levels in the fasting state (5.5 mmol/L) and 2 hours after a 75 g glucose load (8.0 mmol/L) — values that had been published in an unreferenced overview of Australian and European data.1 It advocated future prospective studies, such as those which form the basis of the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) recommendations.2 Contrary to d’Emden et al’s assertions, the 1991 fasting and 2-hour VPG level cut-offs are misaligned. Contemporary data from the 2120 Australian women in the Hyperglycemia and Adverse Pregnancy Outcome study, using the 75 g oral glucose tolerance test, show that 5.5 mmol/L lies at the 98th centile for fasting VPG level, while 8.0 mmol/L corresponds to the 91st centile for 2-hour VPG level (own unpublished data). A recent summary of ambulatory blood glucose monitoring in pregnancy suggested even tighter normative values, with the 97th centiles for fasting blood glucose level (BGL) (4.8 mmol/L) and 2-hour post-meal BGL (6.6 mmol/L) being lower than previous guesstimates.3
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- 1. Martin FI. The diagnosis of gestational diabetes. Ad Hoc Working Party. Med J Aust 1991; 155: 112.
- 2. International Association of Diabetes and Pregnancy Study Groups (IADPSG) Consensus Panel Writing Group; Hyperglycemia and Adverse Pregnancy Outcome Study Steering Committee; Metzger BE, Gabbe SG, Persson B, et al. The diagnosis of gestational diabetes mellitus: new paradigms or status quo? J Matern Fetal Neonatal Med 2012; 25: 2564-2569.
- 3. Hernandez TL, Friedman JE, Van Pelt RE, Barbour LA. Patterns of glycemia in normal pregnancy: should the current therapeutic targets be challenged? Diabetes Care 2011; 34: 1660-1668.
- 4. Crowther CA, Hiller JE, Moss JR, et al. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes. N Engl J Med 2005; 352: 2477-2486.
- 5. Landon MB, Spong CY, Thom E, et al. A multicenter, randomized trial of treatment for mild gestational diabetes. N Engl J Med 2009; 361: 1339-1348.
David McIntyre has received research funding from Novo Nordisk, the National Health and Medical Research Council and the Canadian Institutes of Health Research, and travel assistance and payment for presentations from Novo Nordisk, Sanofi-Aventis, Servier, Sonic Healthcare, AstraZeneca and the Australian Diabetes Educators Association.