Maternal and neonatal outcomes according to the timing of diagnosis of gestational diabetes: A critical appraisal

Table 1 Commonly used gestational diabetes mellitus diagnostic criteria

Ref.1	Diagnostic approach	Standard screening period	GDM diagnosis: PG threshold values in mmol/L, at or above	GDM diagnosis: Criteria before 24 GW	Comments and controversies
O’Sullivan and Mahan[25], 1964	Two step screening, 50 g OCT, if positive, 100 g OGTT	Not specified by the authors	FPG 5, 1-hour PG 9.2, 2-hour PG 6.9, 3-hour PG 7, 2 abnormal values	Not specified by the authors	The first validated test for GDM diagnosis based mainly on future development of type 2 diabetes. No specific data of E-GDM. Controversy on sensitivity of OCT2. 100 g glucose produces gastric discomfort
NDDG, 1979	Two step screening; 50 g OCT, if positive, 100 g OGTT	Not specified by the NDDG	FPG 5.9, 1-hour PG 10.6, 2-hour PG 9.2, 3-hour PG 8.1, 2 abnormal values	Not specified by NDDG	14% change in glucose threshold values, considering the changes in laboratory standards from whole blood to plasma or serum glucose values. Controversy on sensitivity of OCT2. 100 g glucose produces gastric discomfort
Carpenter and Coustan[12], 1982	Two step screening, 50 g OCT, if positive, 100 g OGTT	Not specified by the authors	FPG 5.3, 1-hour 10, 2-hour 8.6, 3-hour 7.8, 2 abnormal values	Not specified by authors	Modification for plasma glucose estimation by glucose oxidase technique. Controversy on sensitivity of OCT2. 100 g glucose produces gastric discomfort. Many organizations recommend C & C criteria for E-GDM screening
IADPSG, 2010, modified 2016	One step, 75 g OGTT	24-28 GW	FPG 5.1, 1-hour PG 10, 2-hour 8.5, one abnormal value	Recommendation of FPG ≥ 5.1 mmol/L in 2010, withdrawn in 2016	Derived from the strong pregnancy outcome data of HAPO study. Concerns about marked increase in GDM prevalence and the cost effectiveness of these criteria. Many countries use these criteria for early pregnancy
WHO, 2013	One step, 75 g OGTT	24-28 GW	FPG 5.1, 1-hour PG 10, 2-hour 8.5, one abnormal value	Recommends same criteria as of 24-28 GW for high-risk women	In 2013, the WHO changed the 1999 criteria, accepting the IADPSG criteria
ADA, 2025	One step, IADPSG, or 2 step C & C criteria	24-28 GW	Either IADPSG or C & C criteria for diagnosis	For high-risk women: FPG 6.1-6.9 mmol/L, HbA1c 41-47 mmol/mol	Approves both IADPSG and C & C criteria, causing confusion among obstetricians/diabetologists. There are major differences in GDM prevalence by these criteria. Does not recommend IADPSG or C & C criteria for use in early pregnancy
ACOG, 2018	Two step screening, 50 g OCT, if positive, 100 g OGTT	24-28 GW	Either C & C criteria or alternative NDDG: FPG 5.8, 1-hour 10.6, 2-hour 9, 2 abnormal values	For high-risk women: Same criteria as for 24-28 GW	All concerns of C & C and NDDG criteria
NICE, 2020	One step screening, screening only for high-risk women, one step 75 g OGTT	24-28 GW	FPG 5.6, 2-hour PG 7.8, one abnormal value	Recommend 75 g OGTT at booking for women with GDM history: Same diagnostic criteria as for 24-28 GW	Mainly used in United Kingdom. Concerns about racial differences in GDM diagnosis by these criteria. Permitted for use in early pregnancy for women with history of GDM only (not for other risks)
CDA, 2018	Two step screening, 50 g OCT, if positive, 75 g OGTT. Alternatively, one step IADPSG criteria	24-48 GW	If 1-hour OCT 111 or 75 g OGTT: FPG 5.3, 1-hour PG 10.6, 2-hour PG 9, one abnormal value	High risk women: Same criteria as for 24-28 GW at any stage in pregnancy	Issues related with sensitivity of screening OCT as with ACOG criteria
Govt of India Guideline, 2018	One step, non-fasting 75 g OGTT	If negative for GDM at booking, rescreen at 24-28 GW	2-hour PG 7.8	Universal screening: 75 g OGTT at booking	Only diagnostic OGTT in non-fasting state. May be of relevance in rural setting. Concerns about the validity of this test
ADIPS, 2013	One step, 75 g OGTT	24-28 GW	FPG 5.1, 1-hour PG 10, 2-hour 8.5, one abnormal value	For high-risk women 75 g OGTT at first opportunity after conception. Same criteria as for 24-28 GW	Criteria same as in IADPSG, but permits its use in early pregnancy

¹The year of last update of the criteria by the author or professional association.

²Screening 50 g oral glucose challenge test can miss 20% gestational diabetes women, especially those with high fasting plasma glucose values.

GDM: Gestational diabetes mellitus; PG: Plasma glucose; GW: Gestational weeks; NDDG: National Diabetes Data Group; IADPSG: International Association of Diabetes in Pregnancy Study group; WHO: World Health Organization; ADA: American Diabetes Association; ACOG: American College of Obstetricians and Gynecologists; NICE: National Institute for Health and Clinical Excellence; CDA: Canadian Diabetes Association; ADIPS: Australasian Diabetes in Pregnancy Society; OCT: Oral glucose challenge test; OGTT: Oral glucose tolerance test; FPG: Fasting plasma glucose; E-GDM: Early-onset gestational diabetes; C & C criteria: Carpenter and Coustan criteria; HbA1c: Glycated hemoglobin A1c; HAPO: Hyperglycemia and Adverse Pregnancy Outcomes.