Evolving concepts around the diagnosis of gestational diabetes

DateObservationsRecommended testDiagnostic criteria for oral glucose challenge test (mmol/L)Prevalence (%)
Fasting blood glucose1 hour2 hour3 hour
1930-40sWomen who later developed (type 2) diabetes had high incidence of large babies and fetal lossNot yet developedNA
1950sThe term “gestational diabetes” introduced for women with poor obstetric histories who during a subsequent pregnancy had high glucose levels on an OGTTOGTT 100 g in high risk patients> 9.4NA
1960sWomen with high risk pregnancies followed postpartum with annual OGTT—a high proportion subsequently developed type 2 diabetesOGTT 100 g in high risk patients (need 2 abnormal values) ≥ 5.0≥ 9.2≥ 8.1≥ 6.92
Whole blood glucose levels
1979-80Missed cases lead American Diabetes Association to recommend universal screening using criteria suggested by National Diabetes Data Group 50 g glucose challenge followed by OGTT 100 g (need 2 abnormal values) ≥ 5.8≥ 10.6≥ 9.2≥ 8.15
1990sModification for using plasma not whole bloodOGTT 100 g (need 2 abnormal values)≥ 5.3≥ 10.0≥ 8.6≥ 7.86
2005-9Randomised controlled trials in women with mild gestational diabetes identified by two step testing show modest benefit of treatment, predominantly on birth weight
2008-10HAPO study shows continuous relation between untreated maternal blood glucose and some primary endpoints but no threshold for markedly increased riskOGTT 75 g, no screening and 1 abnormal value* ≥ 5.1≥ 10.0≥ 8.518
2013Individual countries struggle to come up with guidelines for diagnosis. Shown is the Canadian Diabetes Association preferred approach50 g glucose challenge followed by OGTT 75 g (1 abnormal value)†≥ 5.3≥ 10.6≥ 9.09

OGTT=oral glucose tolerance test, HAPO=Hyperglycemia and Pregnancy Outcome Study.

*International Association of Diabetes in Pregnancy Study Group recommendation based on HAPO.

†Based on data from HAPO but levels associated with a twofold increased risk of birth weight, fetal adiposity, and cord C peptide concentrations being over the 90th centile.