Gestational diabetes: towards an uniform screening strategy
Since long there is lack of international uniformity in the approach to screening and diagnosis of gestational diabetes (GDM). Pregnant women are commonly screened for GDM by a 50g glucose challenge test (GCT) followed by a diagnostic oral glucose tolerance test (100g 3-h OGTT) using the Carpenter & Coustan criteria in late 2nd trimester (two-step screening strategy). Progressively more data emerge that show that the risk of adverse perinatal outcomes are also associated with degrees of hyperglycaemia less severe than overt diabetes during pregnancy. Since 2010 a one-step screening strategy with a 75g OGTT using more stringent criteria to diagnose GDM has been proposed by ‘The International Association of Diabetes and Pregnancy Study Groups’ (IADPSG). Internationally, the IADPSG recommendation for screening for GDM remains controversial since this will lead to an important increase in the number of women labeled and treated as GDM. Other important comments are the paucity of data on the cost-effectiveness of such screening strategy, the uncertainty on the clinical relevance of treatment of mild GDM and the uncertainty on the risk of women who have had mild GDM based on the IADPSG criteria to develop type 2 diabetes postpartum.
Accurate data on the prevalence of GDM are lacking in Belgium and the current practice for screening for GDM varies across different centers. There is also no consensus on screening for GDM in Belgium. The discrepancy in recommendations is due to the lack of data based on research in our own population concerning the best screening strategy for pregestational diabetes in early pregnancy and the lack of data on the best screening strategy for GDM. To address these questions, we started a large Belgian prospective multi-centric cohort study on screening for GDM, the Belgian Diabetes in Pregnancy study (BEDIP-N study). The aim of the study is to recruit 2090 women before 14 weeks of pregnancy. The study is coordinated by UZ Leuven and 6 other centers also participate: Imelda Bonheiden, UZA, OLV-Aalst site Aalst, OLV-Aalst site Asse, St Jan kliniek Brussel and St Jan Brugge. The most important objectives of the study are to evaluate the prevalence of GDM and diabetes early in pregnancy, to evaluate the risk factors for GDM, to evaluate the prevalence of GDM later in pregnancy and to compare the different screening strategies for GDM (screening based on risk factors versus a two-step screening strategy with a GCT or a 1-step approach with a 75g OGTT). In the first trimester all women receive a fasting bloodtest to evaluate the fasting glycemia (FPG). If the FPG shows GDM (FPG=100-125mg/dl) or diabetes (FPG = 126mg/dl or more), women are treated according to normal routine and do not receive any further testing for GDM later in pregnancy. All women with a normal FPG in early pregnancy, undergo testing for GDM between 24-28 weeks with a GCT and 75g OGTT. Both women and health care professionals are blind for the result of the GCT and the diagnosis of GDM is based on the 75g OGTT using the IADPSG criteria. If women are diagnosed with GDM, they are treated according to normal routine. From all women, data on the follow up during pregnancy and pregnancy outcomes are collected. Women with GDM also receive a 75g OGTT three months after the delivery to timely detect (pre)diabetes.