Tests
1st tests to order
one-step test option: 75-g oral glucose tolerance test (OGTT)
Test
Screening for gestational diabetes mellitus (GDM) is performed at 24-28 weeks of gestation and can be performed as a one- or two-step process. There is no consensus among national and international organizations for the optimal approach. The one-step approach simplifies ѕϲrееոiոg by performing only a diagnostic test, typically a fasting 75-g OGTT, in all patients. The International Association of Diabetes and Pregnancy Study Groups (IADPSG) prefers this approach and the American Diabetes Association considers it an acceptable alternative to the two-step approach.[1][49]
The OGTT should be performed in the morning after an overnight fast of at least 8 hours.
Diagnosis of GDM is based upon the finding of one abnormality.[1][49]
Result
any one glucose level: ≥92 mg/dL (≥5.1 mmol/L) fasting; or ≥180 mg/dL (≥10.0 mmol/L) at 1 hour; or ≥153 mg/dL (≥8.5 mmol/L) at 2 hours is considered abnormal
two-step test option: 1-hour 50-g glucose load test (GLT), followed by 3-hour 100-g OGTT
Test
Screening for gestational diabetes mellitus (GDM) is performed at 24-28 weeks of gestation and can be performed as a one- or two-step process. There is no consensus among national and international organizations for the optimal approach. The two-step approach isecommended by the National Institutes of Health, the American College of Obstetricians and Gynecologists (ACOG), and as an alternative approach to the one-step strategy by the American Diabetes Association (ADA).[1][51][50]
In the two-step approach, women undergo a 1-hour 50-g glucose load test (GLT, nonfasting) between 24 and 28 weeks of gestation (women at higher risk should be tested earlier). Glucose levels at 1 hour greater than a threshold of 130, 135, or 140 mg/dL (7.2, 7.5, or 7.8 mmol/L) are suspicious for GDM (ACOG recommends that any of these thresholds can be used); lower thresholds are more sensitive than the 140 mg/dL (7.8 mmol/L) threshold (88% to 99% for 130 mg/dL vs. 70% to 88% for 140 mg/dL) but less specific and more prone to false-positives.[1][51][52] Women with glucose levels greater than the chosen cut-off value following the GLT undergo a 3-hour 100-g OGTT.[1] The OGTT is performed after a minimum 8-hour fast.
Result
1-hour 50-g GLT: glucose >140 mg/dL is considered abnormal; 3 hour 100-g OGTT: two or more plasma glucose levels at or above the following thresholds establish diagnosis: (1) Carpenter/Coustan: ≥95 mg/dL (≥5.3 mmol/L) fasting; ≥180 mg/dL (≥10.0 mmol/L) at 1 hour; ≥155 mg/dL (≥8.6 mmol/L) at 2 hours; ≥140 mg/dL (≥7.8 mmol/L) at 3 hours; (2) National Diabetes Data Group: ≥105 mg/dL (≥5.8 mmol/L) fasting; ≥190 mg/dL (≥10.6 mmol/L) at 1 hour; ≥165 mg/dL (≥9.2 mmol/L) at 2 hours; ≥145 mg/dL (≥8.0 mmol/L) at 3 hours.
Tests to consider
fasting blood (plasma) glucose
Test
For both pregnant and nonpregnant people, a fasting glucose of ≥126 mg/dL (≥7.0 mmol/L) is diagnostic of diabetes.[1] Testing may be confirmed on the immediately subsequent day if glucose elevations are less than unequivocal.[1]
Consider fasting and random glucose testing in women at high risk of GDM or in women with signs or symptoms of hyperglycemia (polyuria, polydipsia, candidiasis, glycosuria, urinary tract infections).
Result
≥126 mg/dL (≥7.0 mmol/L)
random blood (plasma) glucose
Test
In the setting of symptoms concerning for diabetes, a random glucose of ≥200 mg/dL (≥11.1 mmol/L) is diagnostic of diabetes for both pregnant and nonpregnant people.[1] Testing may be confirmed on the next day if glucose elevations are less than unequivocal.[1]
Consider fasting and random glucose testing in women at high risk of gestational diabetes mellitus or in women with signs or symptoms of hyperglycemia (polyuria, polydipsia, candidiasis, glycosuria, urinary tract infections).
Result
≥200 mg/dL (≥11.1 mmol/L)
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