Gestational diabetes – the impending tsunami

For many years, there has been a divergence of opinion as to whether it was worth treating gestational diabetes. This controversy seemed to have been settled following the publication of the ACHOIS study in 2005 which showed that peri-natal complications were lower in the treatment group. In the UK, diagnostic and treatment guidelines for gestational diabetes were published by NICE in 2009 (most clinics use a 2hr oral glucose tolerance test glucose value >7.8mmol/l).

However, at the same time, controversy still existed as to what level of maternal glucose, risk started to rise. The HAPO study published in 2008 demonstrated a continuum of risk for maternal glucose levels and adverse pregnancy outcomes. Given this continuum of risk, the International Association of Diabetes in Pregnancy Study Groups (IADPSG) was created to formulate recommendations for glucose tolerance testing in pregnancy based on the results of the HAPO Study. Given that a continuum of risk was found in HAPO, the recommendations of IADPSG are, of necessity, based on a consensus around an arbitrary decision about odds ratios. The IADPSG guidance for the diagnosis of revolves around a 75g OGTT with glucose measurements fasting and at 1 and 2 hours. GDM is diagnosed with either fasting >5.1mmol/l, 1hr >10mmol/l or 2 hours >8.5mmol/l.

So with an apparent step forward in determining diagnostic criteria, what impact will this have on service provision? Within the UK, various groups have retrospectively examined a cohort of patients who received GTTs during their pregnancies. Compared to current NICE guidance, adoption of the IADSPG criteria will lead to a 50 – 144% increase in the number of women being diagnosed with GDM. This will clearly put a significant strain on services already struggling with screening high risk patients using current criteria – all of this excluding the increasing number of women with Type 2 diabetes of child bearing age requiring pre-conceptual care as well as intensive antenatal care.

Perhaps the updated NICE guidance due in 2015 will be definitive – but there again, perhaps not.

Dr Mark Freeman