Gestational diabetes mellitus

Testing strategies adopt either a one-step method using the 75 g oral glucose tolerance test (OGTT) or a two-step method using a 50 g (non-fasting) glucose load to screen, followed by a 3-hour 100 g fasting OGTT for those who screen positive.[3]American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(Suppl 1):S344-52. https://diabetesjournals.org/care/issue/48/Supplement_1 ​ There is no consensus among national and international organisations for the optimal approach, and the choice generally depends on local customs. See Screening.

UK diagnostic criteria

In the UK, the National Institute for Health and Care Excellence recommends diagnosing gestational diabetes mellitus (GDM) if a pregnant woman has either:[4]National Institute for Health and Care Excellence. Diabetes in pregnancy: management from preconception to the postnatal period. Dec 2020 [internet publication]. https://www.nice.org.uk/guidance/ng3

• Fasting plasma ≥5.6 mmol/L (≥100 mg/dL), or

• 2-hour plasma glucose ≥7.8 mmol/L (≥140 mg/dL) following a 75 g oral glucose load.

International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria (endorsed by the American Diabetes Association [ADA]):[1]Metzger BE, Gabbe SG, Persson B, et al; International Association of Diabetes and Pregnancy Study Groups Consensus Panel. International association of diabetes and pregnancy study groups recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010 Mar;33(3):676-82. http://care.diabetesjournals.org/content/33/3/676.long http://www.ncbi.nlm.nih.gov/pubmed/20190296?tool=bestpractice.com [3]American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(Suppl 1):S344-52. https://diabetesjournals.org/care/issue/48/Supplement_1 ​​

Used to establish diagnosis of GDM using the one-step approach. Diagnosis is made when any one of the following plasma glucose values are exceeded:

• Fasting plasma glucose ≥5.1 mmol/L (≥92 mg/dL)

• 1-hour plasma glucose ≥10.0 mmol/L (≥180 mg/dL) following a 75 g OGTT

• 2-hour plasma glucose ≥8.5 mmol/L (≥153 mg/dL) following a 75 g OGTT.

World Health Organization (WHO) criteria[2]Diagnostic criteria and classification of hyperglycaemia first detected in pregnancy: a World Health Organization Guideline. Diabetes Res Clin Pract. 2014 Mar;103(3):341-63. https://www.doi.org/10.1016/j.diabres.2013.10.012 http://www.ncbi.nlm.nih.gov/pubmed/24847517?tool=bestpractice.com

Alternative one-step test criteria. GDM should be diagnosed at any time in pregnancy if one or more of the following criteria are met:

• Fasting plasma glucose of 5.1 to 6.9 mmol/L (92-125 mg/dL)

• 1-hour plasma glucose ≥10.0 mmol/L (≥180 mg/dL) following a 75 g oral glucose load

• 2-hour plasma glucose 8.5 to 11.0 mmol/L (153-199 mg/dL) following a 75 g oral glucose load.

Fasting and 2-hour plasma glucose levels above these values would indicate overt (rather than gestational) diabetes.

Carpenter and Coustan criteria (endorsed by the ADA and American College of Obstetricians and Gynecologists [ACOG]):[3]American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(Suppl 1):S344-52. https://diabetesjournals.org/care/issue/48/Supplement_1 [51]Committee on Practice Bulletins - Obstetrics. ACOG practice bulletin no. 190: gestational diabetes mellitus. Obstet Gynecol. 2018 Feb;131(2):e49-64. http://www.ncbi.nlm.nih.gov/pubmed/29370047?tool=bestpractice.com

Used to establish diagnosis of GDM using the two-step approach (patients are selected for testing if they have a positive result on an initial glucose load test). Two or more plasma glucose levels at or above the following thresholds on a 3-hour fasting 100 g OGTT establish diagnosis:

• Fasting: ≥5.3 mmol/L (≥95 mg/dL)

• 1 hour: ≥10.0 mmol/L (≥180 mg/dL)

• 2 hours: ≥8.6 mmol/L (≥155 mg/dL)

• 3 hours: ≥7.8 mmol/L (≥140 mg/dL)