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Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy. Geneva: World Health Organization; 2013.

Cover of Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy

Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy.

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2Background

2.1. History of diagnostic criteria for Gestational Diabetes Mellitus (GDM)

The first evidence that screening, diagnosis and treatment of hyperglycaemia in women not previously known to have diabetes improve outcomes was provided by O'Sullivan et al. in the 1960s. After investigating the distribution of plasma glucose values of pregnant women, these authors proposed diagnostic criteria for gestational diabetes based on a 3-h 100g OGTT. They then validated these criteria against the development of future diabetes in the mother11. Further, they tested whether treatment of gestational diabetes improves pregnancy outcomes. To that end, they randomized 613 women with gestational diabetes to receive a specific diet and insulin (307 women) or only a routine diet (306 women)12. The rate of macrosomia was 4.3% in the intervention group compared with 13.1% in the control group. In further support of the importance of detecting and treating gestational diabetes, they reported increased perinatal mortality in offspring of women with gestational diabetes, compared with offspring of women not meeting the diagnostic criteria13. Although the authors recognized that hyperglycaemia per se was perhaps not the only factor causing perinatal mortality, their diagnostic criteria for gestational diabetes gained wide acceptance.

When the 2-h 75g OGTT was established in 1979-1980 by international panels as the diagnostic test for diabetes and glucose intolerance14, the WHO extended this recommendation to pregnant women15. The U.S. National Diabetes Data Group (NDDG) continued to use the 3-h 100g OGTT because the 2-h 75g OGTT had been little investigated during pregnancy14. The American Diabetes Association (ADA) and many other medical associations around the world followed the NDDG recommendation, although often choosing different cut points for detecting glucose abnormalities in pregnancy. This variability was in large part due to difficulties related to converting glucose values from O'Sullivan's studies to their equivalents when glucose was analysed using modern analytic methods in plasma. Over the last 3 decades these procedures and criteria were frequently adopted as a two-step procedure: a 50g 1-h challenge test and then a 100g 3-h OGTT for those positive at screening.

Over the years various definitions of GDM have been proposed by WHO committees15-17. The 1999 report Definition, Diagnosis and Classification of Diabetes Mellitus and its Complications is the most recent WHO report addressing the classification and diagnosis of gestational diabetes3. This report stated:

  • Gestational diabetes is a carbohydrate intolerance resulting in hyperglycaemia of variable severity with onset or first recognition during pregnancy.
  • In the early part of pregnancy (e.g. first trimester and first half of second trimester) fasting and postprandial glucose concentrations are normally lower than in normal, non–pregnant women. Elevated fasting or postprandial plasma glucose levels at this time in pregnancy may well reflect the presence of diabetes which has antedated pregnancy, but criteria for designating abnormally high glucose concentrations at this time have not yet been established.
  • Formal systematic testing for gestational diabetes is usually done between 24 and 28 weeks of gestation.
  • To determine if gestational diabetes is present in pregnant women, a standard OGTT should be performed after overnight fasting (8–14 hours) by giving 75 g anhydrous glucose in 250–300 ml water. Plasma glucose is measured fasting and after 2 hours. Pregnant women who meet WHO criteria for diabetes mellitus or impaired glucose tolerance (IGT) are classified as having GDM. After the pregnancy ends, the woman should be re–classified as having either diabetes mellitus, or IGT, or normal glucose tolerance based on the results of a 75 g OGTT six weeks or more after delivery. The significance of impaired fasting glycaemia (IFG) in pregnancy remains to be established. Any woman with IFG, however, should have a 75 g OGTT.

The HAPO study18, an international multicentre study of a cohort of 25,505 pregnant women tested with a 2-h 75g OGTT and followed through pregnancy, generated an expectation of universal convergence for the adoption of a 75g OGTT for the diagnosis of gestational diabetes, as well as for the formulation of diagnostic criteria for GDM.

In 2008, the International Association of Diabetes and Pregnancy Study Groups (IADPSG) sponsored an International Workshop-Conference on Gestational Diabetes Diagnosis and Classification, to review results of the HAPO and other studies which examined associations of maternal glycaemia and perinatal and long-term outcomes in offspring. Subsequently, the IADPSG Consensus Panel recommended the diagnostic criteria for GDM presented in Table 119. These cut offs represent the average glucose values at which the odds for birth weight > 90th percentile, cord C-peptide > 90th percentile, and neonatal percent body fat >90th percentile reached 1.75 times the odds of these outcomes at the mean glucose values, based on fully adjusted logistic regression models.

These cut points were also recommended by the ADA for a 2-h 75g OGTT in its 2011 position statement.20

2.2. Most commonly used diagnostic criteria for GDM

The most commonly used guidelines for the diagnosis of GDM recommend the following diagnostic criteria (Table 1):

Table 1. Most commonly used guidelines for the diagnosis of GDM.

Table 1

Most commonly used guidelines for the diagnosis of GDM.

2.3. The need to update the 1999 WHO criteria

The diagnostic criteria for hyperglycaemia in pregnancy recommended by WHO in 1999 were not evidence-based, are over 10 years old and needed to be updated in light of new data. An ongoing issue which has been problematic with the 1999 WHO criteria relates to the fasting plasma glucose (FPG) criterion. The diagnostic level of ≥7.0 mmol/l is universally considered to be too high. This has led to some groups using only the 2-h plasma glucose (PG) measurement without measuring FPG while others have used both FPG and 2-h PG measurement. In the latter case, cut points of ≥7.0 mmol/l or ≥6.1mmol/l (levels diagnostic of impaired fasting glucose) have been used.

Copyright © World Health Organization 2013.

All rights reserved. Publications of the World Health Organization can be obtained from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel.: +41 22 791 3264; fax: +41 22 791 4857; e-mail: tni.ohw@sredrokoob). Requests for permission to reproduce or translate WHO publications – whether for sale or for noncommercial distribution – should be addressed to WHO Press, at the above address (fax: +41 22 791 4806; e-mail: tni.ohw@snoissimrep).

Bookshelf ID: NBK169027

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