Gestational Diabetes Screening and Management: What Every Clinician Needs to Know
Clinical Practice Update — Diagnostic Approaches, Glucose Targets, Pharmacotherapy, Fetal Surveillance, and Postpartum Care
This is an original clinical education article informed by current guidelines and evidence. See References below for source documents.
- Clinical Focus
- Screening, diagnosis, glycaemic management, pharmacotherapy, fetal surveillance, delivery timing, and postpartum follow-up for gestational diabetes mellitus
- Target Audience
- Obstetricians, family medicine physicians, endocrinologists, midwives, OB/GYN residents, diabetes educators
- Setting
- Outpatient prenatal clinics, maternal-fetal medicine, endocrinology, primary care
- Source Evidence
- •ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus (2018)
- •ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum (2024)
- •ADA Standards of Care in Diabetes — Chapter 15: Management of Diabetes in Pregnancy (2025)
- •USPSTF Recommendation: Screening for Gestational Diabetes (2021)
- •SMFM Statement: Pharmacological Treatment of Gestational Diabetes (2018, reaffirmed 2024)
- •NICE Guideline [NG3]: Diabetes in Pregnancy (2015, updated 2020)
- •HAPO Study — Hyperglycemia and Adverse Pregnancy Outcomes (NEJM, 2008)
Key Clinical Takeaways
The most important actionable points from this gestational diabetes screening and management Practice Update.
- 1Screen all pregnant patients for gestational diabetes at 24–28 weeks — ACOG recommends the two-step approach as the primary method → Screening
- 2Screen for undiagnosed pregestational diabetes at the first prenatal visit only in patients with risk factors — routine early GDM screening is not recommended → Early Screening
- 3Use Carpenter and Coustan criteria for diagnosis (not NDDG) — the lower thresholds identify patients who benefit from treatment → Diagnosis
- 4Start with medical nutrition therapy and exercise — roughly 70–85% of patients with GDM achieve adequate control with lifestyle alone → Lifestyle Management
- 5Target fasting glucose below 95 mg/dL, 1-hour postprandial below 140 mg/dL, and 2-hour postprandial below 120 mg/dL → Glucose Targets
- 6Insulin is the preferred pharmacotherapy when lifestyle measures fail — ACOG and ADA agree, though SMFM considers metformin a reasonable first-line alternative → Pharmacotherapy
- 7Do not use glyburide in place of insulin — it failed a noninferiority trial and is associated with higher rates of macrosomia and neonatal hypoglycaemia → Pharmacotherapy
- 8Time delivery based on glycaemic control: 39–40+6 weeks for diet-controlled GDM, 39–39+6 weeks for well-controlled medication-requiring GDM → Delivery Timing
- 9Screen for type 2 diabetes at 4–12 weeks postpartum with a 75 g OGTT — or during the delivery hospitalisation as a reasonable alternative → Postpartum Care
- 10The one-step vs two-step debate remains unresolved — ACOG prefers two-step, IADPSG/ADA accept one-step, and outcomes data show no clear winner → Where Guidelines Differ
Who Should Be Screened and When?
Gestational diabetes affects roughly 6–9% of pregnancies in the United States, with rates rising as obesity and type 2 diabetes become more prevalent among reproductive-age individuals. Universal screening at 24–28 weeks remains the cornerstone of detection.
Perform universal gestational diabetes screening at 24–28 weeks of gestation using the two-step approach: a 50 g non-fasting glucose challenge test (GCT) followed by a 100 g 3-hour oral glucose tolerance test (OGTT) if the GCT is positive.
Strong Rec High Evidence ACOG 2018/2024 USPSTF 2021Screen for previously undiagnosed pregestational diabetes before 24 weeks of gestation — preferably at the first prenatal visit — only in patients with risk factors: BMI ≥25 (or ≥23 in Asian Americans), plus one or more of the following: prior GDM, first-degree relative with diabetes, high-risk ethnicity, HbA1c ≥5.7%, prior macrosomic infant, PCOS, or age ≥35.
Strong Rec Moderate Evidence ACOG 2024 ADA 2025Avoid routine screening for GDM before 24 weeks in asymptomatic patients without risk factors. Current evidence does not consistently show that early GDM diagnosis and treatment improves maternal or neonatal outcomes.
Against Moderate Evidence ACOG 2024Consider the one-step 75 g OGTT (IADPSG criteria) as an alternative to the two-step approach based on clinical judgement and institutional protocol. Diagnosis rates are approximately twice as high with the one-step method, but no outcome difference between methods has been demonstrated.
Conditional Rec Moderate Evidence ACOG 2024 USPSTF 2021Comparing Diagnostic Approaches: A Side-by-Side Decision Guide
| Feature | Two-Step (ACOG Preferred) | One-Step (IADPSG/ADA) | Practical Considerations |
|---|---|---|---|
| Step 1 | 50 g GCT (non-fasting); positive if 1-hr glucose ≥130–140 mg/dL (threshold varies by institution) | 75 g OGTT (fasting); single test | GCT is more convenient (no fasting); OGTT requires morning fasting appointment |
| Step 2 | 100 g 3-hr OGTT (fasting); Carpenter and Coustan thresholds: fasting ≥95, 1-hr ≥180, 2-hr ≥155, 3-hr ≥140 mg/dL | N/A — single-step test | 3-hour test is burdensome; no-show rates are high |
| Diagnostic threshold | 2 or more abnormal values on 100 g OGTT | 1 or more abnormal values: fasting ≥92, 1-hr ≥180, 2-hr ≥153 mg/dL | One-step diagnoses roughly twice as many patients (~11.5% vs ~4.9%) |
| Outcome impact | Treatment of GDM diagnosed by two-step reduces PE, macrosomia, shoulder dystocia | Additional diagnoses from lower thresholds have not been shown to improve outcomes vs two-step | USPSTF found no correlation between screening method and pregnancy/neonatal outcomes |
- If using the two-step approach, ACOG recommends Carpenter and Coustan criteria over the higher NDDG thresholds.
- A GCT value ≥200 mg/dL is diagnostic of GDM without the need for a confirmatory 3-hour OGTT at most institutions.
How Should You Manage Gestational Diabetes?
Management begins with lifestyle modification for all patients. Pharmacotherapy is added when glycaemic targets are not met within 1–2 weeks of dietary counselling and exercise.
Initiate medical nutrition therapy (MNT) with referral to a registered dietitian for all patients diagnosed with GDM. Carbohydrate intake should be distributed across three meals and two to three snacks to avoid large glycaemic spikes.
Strong Rec High Evidence ACOG 2018 ADA 2025Prescribe 30 minutes of moderate-intensity aerobic exercise at least 5 days per week (minimum 150 minutes per week). Walking 10–15 minutes after each meal has been shown to improve postprandial glucose levels.
Strong Rec Moderate Evidence ACOG 2018 ADA 2025Monitor self-monitored blood glucose (SMBG) four times daily: fasting and 1 or 2 hours after the start of each meal. Review glucose logs weekly to assess the need for pharmacotherapy.
Strong Rec High Evidence ACOG 2018Start insulin therapy when glucose targets are not consistently met after 1–2 weeks of MNT and exercise. Insulin is the preferred pharmacological agent per ACOG and ADA. Use a combination of a basal insulin (NPH or long-acting analogue) and a rapid-acting analogue (lispro or aspart) titrated to the specific glucose excursion pattern.
Strong Rec High Evidence ACOG 2018 ADA 2025| Measurement | ACOG Target | When to Check | Clinical Tip |
|---|---|---|---|
| Fasting | <95 mg/dL (5.3 mmol/L) | On waking, before eating | Persistently elevated fasting is the strongest predictor of needing insulin |
| 1-hour postprandial | <140 mg/dL (7.8 mmol/L) | 1 hour after the first bite of the meal | Rapid-acting insulin before meals targets postprandial spikes |
| 2-hour postprandial | <120 mg/dL (6.7 mmol/L) | 2 hours after the first bite | Either 1-hr or 2-hr monitoring is acceptable — choose one and be consistent |
Which Medication Should You Choose?
Prescribe insulin as the preferred pharmacological therapy when glycaemic targets are not met with lifestyle measures. Rapid-acting analogues (insulin lispro, insulin aspart) are preferred over regular insulin for mealtime coverage due to more predictable pharmacokinetics. NPH insulin, insulin glargine, and insulin detemir are all available for basal coverage.
Strong Rec High Evidence ACOG 2018 ADA 2025Consider metformin as an alternative if a patient cannot take or declines insulin. Counsel the patient that metformin crosses the placenta, that approximately 25–50% of patients on metformin monotherapy will ultimately require insulin supplementation, and that long-term offspring follow-up data (MiG TOFU study) have raised concerns about higher childhood weight and body fat in some cohorts.
Conditional Rec Moderate Evidence ACOG 2018 SMFM 2018/2024Do not use glyburide in place of insulin. Glyburide failed to demonstrate noninferiority to insulin in a major randomised trial, and meta-analyses have consistently shown higher rates of macrosomia, neonatal hypoglycaemia, and hyperbilirubinaemia compared with insulin. Long-term offspring safety data are lacking.
Against High Evidence ACOG 2018 ADA 2025When Should You Deliver, and What Happens After?
Ensure delivery timing is guided by glycaemic control: diet-controlled GDM (A1GDM) may be managed expectantly to 39 0/7–40 6/7 weeks. Well-controlled medication-requiring GDM (A2GDM) should be delivered at 39 0/7–39 6/7 weeks. Poorly controlled GDM should prompt individualised earlier delivery consideration.
Strong Rec Moderate Evidence ACOG 2018Initiate antenatal fetal surveillance for medication-requiring GDM (A2GDM) starting at 32 weeks. For well-controlled A1GDM without comorbidities, there is no consensus on routine antepartum testing, though many centres begin surveillance at 36–40 weeks or individualise based on clinical factors.
Moderate Rec Low Evidence ACOG 2018Screen for type 2 diabetes at 4–12 weeks postpartum using a 75 g OGTT in all patients who had GDM. As an alternative, performing the 75 g OGTT during the delivery hospitalisation is a reasonable approach and may increase screening rates given that fewer than half of GDM patients complete postpartum testing.
Strong Rec Moderate Evidence ACOG 2024 ADA 2025Counsel patients that GDM significantly increases their lifetime risk of developing type 2 diabetes. Approximately 50% of patients with GDM will develop type 2 diabetes within 5–10 years. Recommend ongoing diabetes screening every 1–3 years and lifestyle modification to reduce risk.
Strong Rec High Evidence ADA 2025 ACOG 2024Clinical Decision Pathway
Evidence in Context
Where ACOG, ADA, and NICE Agree
All three frameworks agree that universal GDM screening at 24–28 weeks is essential, that lifestyle modification is the first-line intervention, that pharmacotherapy should be added when glycaemic targets are not met, and that postpartum screening for type 2 diabetes is critical. All also agree that treating GDM reduces the rates of macrosomia, preeclampsia, shoulder dystocia, and caesarean delivery.
The One-Step vs Two-Step Debate
The HAPO study demonstrated a continuous relationship between maternal glucose and adverse outcomes with no clear threshold, which led the IADPSG to propose lower diagnostic thresholds using the one-step 75 g OGTT. ACOG and the NIH Consensus Conference, however, noted that the one-step approach approximately doubles GDM diagnoses (~11.5% vs ~4.9%) without clear evidence of improved outcomes, raising concerns about overdiagnosis and increased healthcare burden. The USPSTF 2021 review found no correlation between screening method and pregnancy or neonatal outcomes. In practice, approximately 95% of US providers use the two-step method per ACOG recommendations.
Insulin vs Metformin: ACOG and SMFM Disagree
ACOG and ADA recommend insulin as the preferred first-line pharmacotherapy, citing that it does not cross the placenta in meaningful amounts and has the longest safety track record. SMFM (2018, reaffirmed 2024) considers metformin a “reasonable and safe first-line pharmacologic alternative to insulin,” acknowledging that their position differs from ACOG based on how experts weigh the available evidence. The key concerns about metformin include placental transfer with fetal levels equal to maternal levels, a 25–50% monotherapy failure rate requiring insulin addition, and emerging offspring follow-up data suggesting potential increases in childhood BMI. NICE takes a different approach entirely, recommending metformin as first-line and adding insulin only if metformin fails.
Postpartum Testing: The 2024 ACOG Update
The 2024 ACOG Clinical Practice Update changed the postpartum screening window from 6–12 weeks to 4–12 weeks and introduced inpatient testing during the delivery hospitalisation as a reasonable alternative. This change was driven by the reality that fewer than half of GDM patients return for postpartum glucose testing. Barriers include transportation, childcare, loss of insurance, and competing priorities of early motherhood. Performing the 75 g OGTT before discharge captures patients who might otherwise be lost to follow-up.
What We Still Don’t Know
References
- 1.ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol. 2018;131(2):e49–e64. doi:10.1097/AOG.0000000000002501
- 2.Gandhi M, Kaimal A, Turrentine M, et al. ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum. Obstet Gynecol. 2024;144(1):e20–e23. doi:10.1097/AOG.0000000000005612
- 3.US Preventive Services Task Force. Screening for Gestational Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;326(6):531–538. doi:10.1001/jama.2021.11922
- 4.American Diabetes Association Professional Practice Committee. 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2025. Diabetes Care. 2025;48(Suppl 1):S306–S320. doi:10.2337/dc25-S015
- 5.Society for Maternal-Fetal Medicine. SMFM Statement: Pharmacological treatment of gestational diabetes. Am J Obstet Gynecol. 2018;218(5):B2–B4. doi:10.1016/j.ajog.2018.01.041 (Reaffirmed 2024)
- 6.HAPO Study Cooperative Research Group. Hyperglycemia and adverse pregnancy outcomes. N Engl J Med. 2008;358(19):1991–2002. doi:10.1056/NEJMoa0707943
- 7.Landon MB, Spong CY, Thom E, et al. A multicenter, randomized trial of treatment for mild gestational diabetes. N Engl J Med. 2009;361(14):1339–1348. doi:10.1056/NEJMoa0902430
- 8.NICE Guideline [NG3]. Diabetes in pregnancy: management from preconception to the postnatal period. 2015, updated 2020. nice.org.uk/guidance/ng3
How to Read the Evidence Tags
Every recommendation carries two tags. These are Medaptly’s own simplified interpretations for educational clarity.
Recommendation Strength
| Tag | What It Means | In Practice |
|---|---|---|
| Strong Rec | Benefits clearly outweigh risks for most patients. | Standard practice. |
| Moderate Rec | Evidence favours benefit; some uncertainty remains. | Most patients should receive this. |
| Conditional Rec | Benefit depends on individual circumstances. | Shared decision-making. |
| Against | No benefit or potential harm. | Avoid. |
Evidence Quality
| Tag | What It Means | Confidence |
|---|---|---|
| High Evidence | Multiple RCTs or high-quality meta-analyses. | Very confident. |
| Moderate Evidence | Single RCT or large observational studies. | Reasonably confident. |
| Low Evidence | Expert consensus or small studies. | Less certain. |
These are Medaptly’s simplified interpretations. For full classification systems, consult the original documents in References.