GD Screening Changes Coming in 2027: What to Expect

How we screen for gestational diabetes has been debated for decades—and 2027 may bring significant changes. The tension between the ACOG-preferred two-step approach and the internationally used one-step approach remains unresolved, new research is building the case for first-trimester screening in high-risk women, and the 2026 ADA Standards of Care have already incorporated updated language that may foreshadow upcoming ACOG revisions. Here's what you need to know.

The Current Screening Landscape (2026)

There are currently two dominant approaches to gestational diabetes screening in the United States:

The Two-Step Approach (ACOG Preferred)

Step 1: 50g non-fasting glucose challenge test (GCT) at 24-28 weeks

• No fasting required
• Blood drawn 1 hour after drinking 50g glucose solution
• Threshold for positive: typically ≥130 or ≥140 mg/dL (varies by lab)
• GD diagnosis rate at this step: approximately 15-25% of women "fail" and require Step 2

Step 2 (for those who fail Step 1): 100g 3-hour oral glucose tolerance test (OGTT)

• Fasting required (overnight)
• Blood drawn fasting and at 1, 2, and 3 hours
• GD diagnosed if 2 or more values meet or exceed thresholds (Carpenter-Coustan criteria): fasting ≥95, 1hr ≥180, 2hr ≥155, 3hr ≥140 mg/dL
• Overall GD diagnosis rate: approximately 4.9% using this approach

The One-Step Approach (IADPSG/Increasingly ADA-Supported)

Single test: 75g 2-hour OGTT at 24-28 weeks

• Fasting required
• Blood drawn fasting and at 1 and 2 hours
• GD diagnosed if ANY single value meets or exceeds: fasting ≥92, 1hr ≥180, 2hr ≥153 mg/dL
• Only ONE abnormal value needed (vs. two for ACOG two-step)
• Overall GD diagnosis rate: approximately 11.5%—more than double the two-step rate

Why This Debate Has Been Going on for 20+ Years

The core tension is between sensitivity and specificity, and between diagnosing enough to help versus diagnosing so many that intervention resources are overwhelmed:

The Case for One-Step

• More sensitive—catches women with milder glucose intolerance who still benefit from management
• Simpler for patients (one visit vs. two)
• Used by most countries outside the US, facilitating international research comparison
• The HAPO study, which validated the one-step criteria, showed linear increases in adverse outcomes across the glucose spectrum—supporting intervention at lower thresholds
• The 2026 ADA Standards increasingly favor this approach

The Case for Two-Step

• Lower diagnosis rate means fewer women receive a potentially stigmatizing label and intervention burden
• A large NEJM pragmatic trial (GESTALT) found similar perinatal outcomes between one-step and two-step approaches when women received standard of care treatment
• The two-step approach identifies a more distinctly hyperglycemic population
• Long-term data on whether treating the additional cases identified by one-step approach meaningfully improves outcomes is still evolving
• ACOG continues to support the two-step approach pending stronger evidence for benefit of treating milder cases

The 2026 ADA Standards: Moving Toward One-Step?

The 2026 ADA Standards of Care (published January 2026) made several notable updates regarding GD screening:

• The standards acknowledge both approaches but include updated narrative language leaning toward the one-step IADPSG criteria having clinical utility
• New discussion of early GD screening in high-risk women was expanded
• Guidance on managing women diagnosed with mild glucose intolerance (the "new" cases the one-step approach captures) was updated

This sets the stage for a potential ACOG guideline revision in 2026-2027 that might give greater flexibility or formal recommendation to the one-step approach.

Early Screening: The First Trimester Frontier

One of the most significant developments in gestational diabetes research is growing evidence for first-trimester screening in high-risk women. Current standard practice screens all women at 24-28 weeks. But emerging research suggests:

• Women with GD diagnosed before 20 weeks represent a different, higher-risk group (possibly undiagnosed pre-existing diabetes)
• First-trimester fasting glucose ≥92 mg/dL predicts GD diagnosis at 24-28 weeks
• Early intervention (before 20 weeks) in high-risk women may prevent some GD development or reduce severity
• HbA1c ≥5.7% in the first trimester identifies women at very high risk

What's being studied for potential 2027 guidance:

• Universal HbA1c at first prenatal visit to screen for pre-existing undiagnosed diabetes
• Early 75g OGTT at 12-16 weeks for women with risk factors (BMI ≥30, prior GD, family history)
• Fasting glucose at first visit as a risk stratification tool

Diagnostic Criteria: Are the Numbers Right?

Another area of ongoing debate is whether the current diagnostic thresholds are optimal. Some researchers argue:

• The Carpenter-Coustan thresholds (used in the two-step approach) were based on risk of maternal diabetes, not perinatal outcomes
• The IADPSG thresholds (used in the one-step approach) were derived from the HAPO study's perinatal outcome data—a more evidence-based foundation
• Some researchers advocate for lower thresholds still, arguing that any glucose elevation above normal confers risk

A 2026 guideline revision from either ACOG or USPSTF (US Preventive Services Task Force) could potentially update these thresholds based on newer outcome data.

What Could Change in 2027?

Based on the current trajectory of evidence and policy discussions, potential 2027 changes include:

1. ACOG may formally endorse both one-step and two-step approaches as equally valid options rather than preferring two-step
2. Early screening guidance for high-risk women (prior GD, BMI ≥30, age 35+) at 12-16 weeks may be added
3. Universal first-trimester HbA1c to catch pre-existing undiagnosed diabetes may become standard
4. Harmonization with international guidelines may lead the US to move toward the IADPSG one-step approach for uniformity

What This Means for You Right Now

If you are currently pregnant or planning to become pregnant:

• Know your risk factors and ask about early screening if you have prior GD, high BMI, advanced maternal age, or strong family history
• Understand which screening method your provider uses and what the diagnostic criteria are—this affects whether you'll be diagnosed with a borderline result
• A positive screen is not the same as a diagnosis—a failed 50g GCT (Step 1) requires the 3-hour OGTT for confirmation
• Even "borderline" results matter—even glucose levels below the diagnostic threshold are associated with increased risk of complications, and lifestyle modifications are still beneficial

For related reading, see our article on new GD guidelines in 2026 and our overview of the latest GD research findings.

This content is for informational purposes only and is not medical advice. Always consult your healthcare provider or registered dietitian for personalized guidance.