Many approaches to detection and diagnosis of GDM have been proposed. The criteria for GDM were originally set based on the power to detect women at risk for development of diabetes mellitus outside of pregnancy in later years 1 . Some of the criteria that have been proposed subsequently are based on the distribution of glucose values from oral glucose tolerance tests performed in other population samples of women during the last half of gestation. The high risk of progression to diabetes mellitus following GDM has been confirmed extensively among many different racial/ethnic groups. Several important studies have shown that the development of type 2 diabetes can be prevented or delayed by intervention with lifestyle changes or medications. Importantly, women with GDM were included among those recruited as subjects for the Diabetes Prevention Program 2 in the USA. Women with previous GDM represented the target population that was used for the Troglitazone in the Prevention of Diabetes (TRIPOD) intervention trial 3 , also in the USA.
Risk to offspring
It is also recognized that intrauterine exposure to the altered metabolic environment of diabetes or GDM is associated with increased risk of obesity and abnormal glucose metabolism during childhood and adult life in the offspring, thus, contributing to the progressive increase of obesity, GDM and type 2 diabetes in the population (see Figure). However, to date, the extent to which GDM adds to the risk of diabetes has been estimated in only one population, the Pima Indians of Arizona.
Diabetes begets diabetes
| IGT | impaired glucose tolerance |
| PGDM | pre-gestational diabetes mellitus |
Adverse pregnancy outcome
Interest in the detection of GDM for the purpose of identifying pregnancies in which there may be increased risk of adverse perinatal outcome, for the most part, developed after the diagnostic criteria had been established. Consequently, one major source of controversy about GDM derives from uncertainty about what level of maternal hyperglycaemia is associated with a significant risk of adverse pregnancy outcome.
There is general agreement that overt diabetes, diagnosed prior to pregnancy, clearly increases the risk of adverse pregnancy outcome. What is yet to be established is the level of glucose intolerance short of diabetes that is associated with significantly increased risk. The currently ongoing multicentre, international Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study is designed to address this issue 4 . The collection of clinical data in the HAPO study was completed in 2006, and initial results were presented at a HAPO Study Symposium during the June 2007 American Diabetes Association Annual Scientific Meeting.
In the meantime it is recommended that clinicians and investigators who currently have programmes in place for the diagnosis and treatment of GDM continue to use their present paradigms or adopt the recommendations that were made by the participants in the Fourth International Workshop Conference on Gestational Diabetes Mellitus 5 and recently endorsed by the Fifth International Workshop Conference on GDM 6 .
1.O'Sullivan,J.B. Mahan,C.M. Criteria for the oral glucose tolerance test in pregnancy. Diabetes.1964; 13: 278-285
2.Diabetes Prevention Research Group Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Eng J Med.2002; 346: 393-403
3.Buchanan,T.A. Xiang,A.H. Peters,R.K. Kjos,S.L. Marroquin,A. Goico,J. Ochoa,C. Tan,S. Berkowitz,K. Hodis,H.N. Azen,S.P. Preservation of pancreatic beta-cell function and prevention of type 2 diabetes by pharmacological treatment of insulin resistance in high-risk hispanic women. Diabetes.2002; 51(9): 2796-803
4.HAPO Study Cooperative Research Group The Hyperglycaemia and adverse pregnancy Outcome (HAPO) Study. Int J Gynaecol Obstet.2002; 78(1): 69-77
5.Metzger,B.E. Coustan,D.R. Summary and recommendations of the Fourth International Workshop-Conference on Gestational Diabetes Mellitus. The Organizing Committee. Diabetes Care.1998; 21 Suppl 2: B161-B167
6.Metzger,B.E. et al. Summary and recommendations of the Fifth International Workshop-Conference on Gestational Diabetes Mellitus. In Preparation
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