Defining gestational diabetes: not just about cutoffs

The criteria for diagnosing gestational diabetes, defined as hyperglycaemia less than overt diabetes first detected in pregnancy, 1 International Association of Diabetes and Pregnancy Study Groups Consensus PanelInternational association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010; 33: 676-682 Crossref PubMed Scopus (3303) Google Scholar vary globally. The International Association of Diabetes in Pregnancy Study Groups (IADPSG), informed by the large international Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study (n=25 505), 2 HAPO Study Cooperative Research GroupHyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008; 358: 1991-2002 Crossref PubMed Scopus (4106) Google Scholar sought diagnostic consensus in 2010. 1 International Association of Diabetes and Pregnancy Study Groups Consensus PanelInternational association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010; 33: 676-682 Crossref PubMed Scopus (3303) Google Scholar A global oral glucose tolerance test (OGTT) diagnostic approach was proposed on the basis of the relationship between maternal OGTT glucose values at 24–28 weeks' gestation and perinatal complications. By contrast, the O'Sullivan approach (and its derivative, the Carpenter and Coustan criteria), 3 Sweeting A Wong J Murphy HR Ross GP A clinical update on gestational diabetes mellitus. Endocr Rev. 2022; 43: 763-793 Crossref PubMed Scopus (67) Google Scholar is based on small studies aligning gestational diabetes prevalence to background diabetes prevalence in the non-pregnant population (n=752). This method was validated with a post-partum follow-up study of the excess maternal risk of future type 2 diabetes (n=1013), which, by 22–25 years' follow-up, reported a relative risk of 6·64 (95% CI 4·19–10·52). 4 Bellamy L Casas JP Hingorani AD Williams D Type 2 diabetes mellitus after gestational diabetes: a systematic review and meta-analysis. Lancet. 2009; 373: 1773-1779 Summary Full Text Full Text PDF PubMed Scopus (2414) Google Scholar Concern over the predicted increase in the number of women diagnosed with gestational diabetes with the IADPSG approach (an increase of 75% 5 Saeedi M Cao Y Fadl H Gustafson H Simmons D Increasing prevalence of gestational diabetes mellitus when implementing the IADPSG criteria: a systematic review and meta-analysis. Diabetes Res Clin Pract. 2021; 172108642 Summary Full Text Full Text PDF Scopus (60) Google Scholar ) led to continuation of O'Sullivan-derived approaches in many countries. However, the differences between the IADPSG and the O'Sullivan approaches extend beyond the rationale behind diagnosing gestational diabetes (IADPSG for perinatal diabetes vs O'Sullivan for future maternal diabetes) and diagnostic glucose cutoffs. There are also major differences in practical application, including glucose load (75 g vs 100 g), duration (2 h vs 3 h), number of samples needed for diagnosis (one vs two), and preceding screening (none vs 50 g glucose challenge test [GCT]). Glucose intolerance in pregnancy and risk of early-onset type 2 diabetes: a population-based cohort studyGestational glucose intolerance, including conditions not meeting gestational diabetes criteria of the two-step strategy, confers a high risk of type 2 diabetes in young adulthood. These conditions should be recognised as risk factors for type 2 diabetes, especially among women with abnormal fasting glucose concentrations during pregnancy. Full-Text PDF