The evidence grading system for clinical practice recommendations (A through C, E) is defined at the end of the "Major Recommendations" field.
Detection and Diagnosis of Gestational Diabetes Mellitus (GDM)
- Screen for GDM using risk factor analysis and, if appropriate, use of an oral glucose tolerance test (OGTT). (C)
- Women with GDM should be screened for diabetes 6 to 12 weeks postpartum and should be followed up with subsequent screening for the development of diabetes or pre-diabetes. (E)
Screening for and Diagnosis of GDM
Carry out GDM risk assessment at the first prenatal visit.
Women at very high risk for GDM should be screened for diabetes as soon as possible after the confirmation of pregnancy. Criteria for very high risk are:
- Severe obesity
- Prior history of GDM or delivery of large-for-gestational-age infant
- Presence of glycosuria
- Diagnosis of polycystic ovarian syndrome (PCOS)
- Strong family history of type 2 diabetes
Screening/diagnosis at this stage of pregnancy should use standard diagnostic testing (see the National Guideline Clearinghouse [NGC] summary of American Diabetes Association [ADA] guideline Standards of medical care in diabetes. I. Classification and diagnosis).
All women of higher than low risk of GDM, including those above not found to have diabetes early in pregnancy, should undergo GDM testing at 24 to 28 weeks of gestation.
Low risk status, which does not require GDM screening, is defined as women with all of the following characteristics:
- Age <25 years
- Weight normal before pregnancy
- Member of an ethnic group with a low prevalence of diabetes
- No known diabetes in first-degree relatives
- No history of abnormal glucose tolerance
- No history of poor obstetrical outcome
Two approaches may be followed for GDM screening at 24 to 28 weeks:
- Two-step approach:
- Perform initial screening by measuring plasma or serum glucose 1 h after a 50-g oral glucose load. A glucose threshold after 50-g load of >140 mg/dL identifies ~ 80% of women with GDM, while the sensitivity is further increased to ~ 90% by a threshold of >130 mg/dL.
- Perform a diagnostic 100-g OGTT on a separate day in women who exceed the chosen threshold on 50-g screening.
- One-step approach (may be preferred in clinics with high prevalence of GDM): Perform a diagnostic 100-g OGTT in all women to be tested at 24 to 28 weeks.
The 100-g OGTT should be performed in the morning after an overnight fast of at least 8 h.
A diagnosis of GDM requires at least two of the following plasma glucose values:
- Fasting: >95 mg/dL (>5.3 mmol/L)
- 1 h: >180 mg/dL (>10.0 mmol/L)
- 2 h: >155 mg/dL (>8.6 mmol/L)
- 3 h: >140 mg/dL (>7.8 mmol/L)
For information on the National Diabetes Education Program (NDEP) campaign to prevent type 2 diabetes in women with GDM, go to www.ndep.nih.gov/diabetes/pubs/NeverTooEarly_Tipsheet.pdf.
Definitions:
American Diabetes Association's Evidence Grading System for Clinical Practice Recommendations
A
Clear evidence from well-conducted, generalizable, randomized controlled trials that are adequately powered, including:
- Evidence from a well-conducted multicenter trial
- Evidence from a meta-analysis that incorporated quality ratings in the analysis
- Compelling non-experimental evidence (i.e., "all or none" rule developed by the Center for Evidence Based Medicine at Oxford*)
Supportive evidence from well-conducted randomized, controlled trials that are adequately powered, including:
- Evidence from a well-conducted trial at one or more institutions
- Evidence from a meta-analysis that incorporated quality ratings in the analysis
*Either all patients died before therapy and at least some survived with therapy, or some patients died without therapy and none died with therapy. Example: use of insulin in the treatment of diabetic ketoacidosis.
B
Supportive evidence from well-conducted cohort studies, including:
- Evidence from a well-conducted prospective cohort study or registry
- Evidence from a well-conducted meta-analysis of cohort studies
Supportive evidence from a well-conducted case-control study
C
Supportive evidence from poorly controlled or uncontrolled studies, including:
- Evidence from randomized clinical trials with one or more major or three or more minor methodological flaws that could invalidate the results
- Evidence from observational studies with high potential for bias (such as case series with comparison with historical controls)
- Evidence from case series or case reports
Conflicting evidence with the weight of evidence supporting the recommendation
E
Expert consensus or clinical experience
