Poster Australasian Diabetes in Pregnancy Annual Scientific Meeting 2013

Pregnancy outcomes based on old and new diagnostic criteria for GDM – are we over or under-diagnosing women? (#111)

Judy Luu 1 , Shamasunder Acharya 1 , Kannan Bakthavatsalam 2 , Alessandra Bisquera 3 , John Attia 1 3
  1. John Hunter Hospital, New Lambton, NSW, Australia
  2. Diabetes, Blacktown Hospital, Blacktown, NSW, Australia
  3. Clinical Research Design, IT and Statistical Support, Hunter Medical Research Institute, Newcastle, NSW, Australia

Gestational diabetes mellitus (GDM) historically complicates 3-14% of all pregnancies. Prior to 2010, the diagnostic criteria for GDM was a fasting blood glucose level above 5.5 mmol/L fasting or above 8.0mmol/L 2 hours following a 75g oral glucose load (1). Based on the Hyperglycaemia and Adverse Pregnancy Outcomes (HAPO) study (2) the International Association of Diabetes and Pregnancy Study Groups (IADPSG) proposed new guidelines for the diagnosis of GDM in 2010 (3). These recommended a 75 g oral glucose tolerance test for all women not already known to be diabetic at 24–28 weeks of gestation with GDM diagnosed if blood glucose levels exceeded 5.1mmol/L fasting, 10.0 mmol/L after 1 hour and 8.5mmol/L after 2 hours. Early studies indicate that the new criteria may result in 21-31% more pregnancies being labelled as GDM (4).

To evaluate the benefit of adopting the new IADPSG recommendations, we retrospectively studied pregnancy outcomes in all pregnant women who undertook a 75g OGTT over an 18 month period in 2009-2011 through the Hunter Area Pathology Service. We compared pregnancy outcomes for women using both the old and new criteria. Our results showed that the majority of women (85%) would be identified as having normal glucose tolerance on both criteria (Group A), 5% would be classified as GDM on the new criteria only (Group B) and 2.7% would be classified as GDM based on old criteria only (Group C) with 7.1% identified as GDM on both criteria (Group D).

Poisson regression, adjusted for gestational age and maternal age, indicated that those who tested positive on current ADIPS but not proposed IADPSG criteria (group C) or vice versa had adverse events rates similar to women classified as GDM on both criteria and significantly higher than women with normal glucose tolerance (Table 1).

Our study confirms that our current criteria for GDM misses many women with adverse outcomes.  Using the new IADPSG criteria will identify more women with GDM but will miss 18% of women who are currently being treated as GDM.  These women also carry an increased risk of adverse events and further studies are needed.

  1. Hoffman L, Nolan C, Wilson JD, Oats JJN & Simmons D 1998. Gestational diabetes mellitus-management guidelines: The Australasian Diabetes in Pregnancy Society. Medical Journal of Australia 169:93–97.
  2. The HAPO Study Cooperative Research Group. Hyperglycemia and adverse pregnancy outcomes. N Engl J Med 2008;358:19912002.
  3. International Association of Diabetes and Pregnancy Study Groups Consensus Panel, Metzger BE, Gabbe SG, Persson B, Buchanan TA, Catalano PA, Damm P, et al. International association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care 2010;33:676–82.
  4. Flack JR, Ross GP, Ho S, McElduff A. Recommended changes to diagnostic criteria for gestational diabetes: Impact on workload. Aust N Z J Obstet Gynaecol. 2010 Oct;50(5):439-43.