IADPSG Criteria for Gestational Diabetes
The IADPSG (International Association of Diabetes and Pregnancy Study Groups) recommends a one-step diagnostic approach using a 75-g oral glucose tolerance test (OGTT) at 24-28 weeks of gestation, with GDM diagnosed when ANY ONE of three plasma glucose thresholds is met or exceeded. 1
Diagnostic Criteria
One-Step Strategy (IADPSG)
Perform a 75-g OGTT after an overnight fast of at least 8 hours at 24-28 weeks of gestation. GDM is diagnosed when ANY of the following plasma glucose values are met or exceeded: 1, 2
- Fasting: ≥92 mg/dL (5.1 mmol/L)
- 1-hour: ≥180 mg/dL (10.0 mmol/L)
- 2-hour: ≥153 mg/dL (8.5 mmol/L)
This differs fundamentally from older criteria by requiring only one abnormal value rather than two, which increases GDM diagnosis rates from 5-6% to 15-20% 1. These thresholds were derived from the HAPO study, identifying glucose levels at which odds for adverse outcomes reached 1.75 times the mean population risk 2.
Early Pregnancy Screening
Test for undiagnosed type 2 diabetes at the first prenatal visit in women with risk factors using fasting plasma glucose, HbA1c, or random plasma glucose 3. If overt diabetes is found (fasting glucose ≥126 mg/dL, 2-hour glucose ≥200 mg/dL, or HbA1c ≥6.5%), manage as preexisting diabetes 4.
If early screening shows fasting glucose 92-125 mg/dL (5.1-6.9 mmol/L), diagnose as GDM even before 24 weeks 4, 5. However, the IADPSG criteria were not validated for use before 24 weeks, so routine early OGTTs are not recommended unless risk factors are present 2.
Management Recommendations
Initial Treatment Approach
Begin with medical nutrition therapy and daily moderate exercise for 30 minutes or more 4. This is the cornerstone of GDM management, and 80-90% of women diagnosed by IADPSG criteria can achieve glycemic control with lifestyle modifications alone 1, 6.
Glycemic Targets
Target the following blood glucose levels 4, 6:
- Fasting: <95 mg/dL (5.3 mmol/L)
- 1-hour postprandial: <140 mg/dL (7.8 mmol/L) OR
- 2-hour postprandial: <120 mg/dL (6.7 mmol/L)
Self-monitoring should occur before meals and either 1 or 2 hours after the start of each meal 4.
Pharmacologic Therapy
Add insulin if lifestyle therapy fails to maintain normoglycemia 4. Insulin is the first-line pharmacologic agent because it does not cross the placenta to a measurable extent 6.
Do not use metformin or glyburide as first-line agents 6. Both cross the placenta, lack long-term safety data, and fail to provide adequate glycemic control in 23-28% of women 6.
Postpartum Care
Perform a 75-g OGTT at 6-12 weeks postpartum to screen for persistent diabetes or prediabetes using standard non-pregnancy diagnostic criteria 4. Monitor fasting plasma glucose or self-monitored blood glucose for 24-72 hours after delivery to rule out ongoing hyperglycemia 4.
Continue lifelong screening for diabetes or prediabetes at least every 3 years 3. Women with prediabetes should receive intensive lifestyle interventions or metformin to prevent diabetes 3.
Evidence Quality and Controversy
The IADPSG criteria remain somewhat controversial. While they identify women at increased risk for adverse outcomes including large-for-gestational-age births and preeclampsia 1, 7, a randomized trial comparing one-step (IADPSG) versus two-step methods found no difference in pregnancy complications despite diagnosing twice as many women with GDM 1.
However, treatment of GDM diagnosed by IADPSG criteria demonstrably reduces excessive fetal growth 8, with odds ratios for large-for-gestational-age and macrosomia of 2.81 and 2.84 respectively in untreated women, but no increased risk in treated women 8. One observational study showed improved outcomes including lower rates of preeclampsia (1.0% vs 2.2%), labor induction (25.6% vs 32.8%), and NICU admission (4.8% vs 8.5%) after adopting IADPSG criteria 9.
The ADA recommends IADPSG criteria specifically because they are the only ones based on pregnancy outcomes rather than prediction of subsequent maternal diabetes 1. Long-term data from HAPO Follow-up Study demonstrate that maternal hyperglycemia diagnosed by IADPSG criteria predicts offspring glucose intolerance, adiposity, and metabolic dysfunction at 10-14 years of age 1.