Gestational%20diabetes%20mellitus Diagnosis
Diagnosis
Overt Diabetes Mellitus (DM)
- Diabetes diagnosed in the 1st trimester of pregnancy is classified as pre-existing pregestational diabetes
- Overt DM may be found in women presenting with risk factors for type 2 diabetes during the 1st prenatal visit (before 13 weeks of gestation)
- Risk factors for type 2 DM include:
- Overweight
- Physically inactive
- History of gestational diabetes mellitus (GDM)
- With hypertension, history of CVD, or polycystic ovary syndrome, acanthosis nigricans
- HDL cholesterol level 0.90 mmol/L (<35 mg/dL) and/or triglyceride level 2.82 mmol/L (>250 mg/dL)
- With previous test result that showed HbA1c ≥5.7%, impaired glucose tolerance or impaired fasting glucose
- With DM in 1st-degree relative
- Glycosuria at 1st prenatal visit
- Diagnostic criteria for overt DM and GDM at the 1st prenatal visit in women not known to have diabetes include a fasting plasma glucose (FPG) of ≥7 mmol/L (≥126 mg/dL) for overt DM and 5.1-6.9 mmol/L (92-125 mg/dL) for GDM
- Other criteria for overt DM include an HbA1c level of ≥6.5% and a random plasma glucose of ≥11.1 mmol/L (≥200 mg/dL)
- Women who may be at risk of pre-pregnancy DM should be offered a 75-g oral glucose tolerance test (OGTT) at 24-28 weeks of gestation if initial screening test is negative
Screening/Diagnosis of Gestational Diabetes Mellitus (GDM)
- Uses either the “one-step” or “two-step” approach
- Performed at 24-28 weeks of gestation in women without previous diagnosis of overt diabetes
- Consider offering the 75-g OGTT to women with clinical features of maternal hyperglycemia or those with risk factor but presented after 28 weeks of gestation
“One-step” Approach
- Diagnostic criterion recommended by WHO
- A 75-g oral glucose tolerance test (OGTT) is performed after an overnight fasting of 8-14 hours
- Perform OGTT in the morning after an overnight fasting of at least 8 hours
- Plasma glucose measurement at fasting and at 1 and 2 hours
- Diagnosis of GDM1 is made when any 1 of the following is present:
- FPG 5.1-6.9 mmol/L (92-125 mg/dL)
- 1-hour plasma glucose ≥10 mmol/L (≥180 mg/dL)
- 2-hour plasma glucose 8.5-11 mmol/L (153-199 mg/dL)
- OGTT should be repeated 4-6 weeks later in patients with initial normal results
- May also be offered at 24-28 weeks in women with previous GDM
- Diagnostic criteria for overt DM using a 75-g 2-hour OGTT at 24-28 weeks of gestation are an FPG of ≥7 mmol/L (126 mg/dL) and a 2-hour plasma glucose of ≥11.1 mmol/L (200 mg/dL) 1National Institute of Health and Care Excellence 2015 guideline value for diagnosis of GDM with a 75-g 2-hour OGTT includes an FPG of ≥5.6 mmol/L or a 2-hour plasma glucose of ≥7.8 mmol/L
“Two-step” Approach
- Diagnostic criterion recommended by the American Congress of Obstetricians and Gynecologists (ACOG)
- A 50-g glucose 1-hour challenge test (non-fasting) followed by a 100-g 3-hour OGTT (fasting) for those with positive screen
- Perform 100-g OGTT if the 1-hour plasma glucose level is ≥7.2, 7.5 or 7.8 mmol/L (≥130, 135, or 140 mg/dL)
- Diagnosis of GDM is made when at least 2 of the following are present:
- FPG ≥5.3 mmol/L (≥95 mg/dL)
- 1-hour plasma glucose ≥10 mmol/L (≥180 mg/dL)
- 2-hour plasma glucose ≥8.6 mmol/L (≥155 mg/dL)
- 3-hour plasma glucose ≥7.8 mmol/L (≥140 mg/dL)
Postpartum Screening
- All women who will be identified to have overt DM during pregnancy or have GDM should have postpartum glucose testing
- Women with GDM should be screened for persistent DM 4-12 weeks postpartum as the risk of developing maternal type 2 diabetes is increased after pregnancy and also because GDM may be an undiagnosed pre-existing type 1 or 2 diabetes
- Probability of progression to DM is high with the following postnatal test results: Impaired glucose tolerance with 75-g OGTT, HbA1c 5.7-6.4%, FPG 5.7-6.9 mmol/L
- Uses the fasting plasma glucose test and nonpregnancy diagnostic criteria
- A 75-g 2-hour OGTT is not routinely offered in women with normal postpartum blood glucose levels
- A1c is not advised for diagnosis of postpartum-persistent diabetes; may be offered at 1 year postpartum in women with GDM who have negative postnatal test for diabetes
- Lifelong screening for development of DM or prediabetes at least every 3 years is recommended to all women with history of GDM with screening frequency depending on other risk factors
- Women with GDM should be screened for persistent DM 4-12 weeks postpartum as the risk of developing maternal type 2 diabetes is increased after pregnancy and also because GDM may be an undiagnosed pre-existing type 1 or 2 diabetes