SUMMARY:

ACOG released updated guidance on gestational diabetes (GDM), which has become increasingly prevalent worldwide.  Class A1GDM refers to diet-controlled GDM. Class A2GDM refers to the clinical scenario where medications are required. Highlights and changes from the previous practice bulletin include the following:

• Screening for GDM – One or Two Step?
• Who Should be Screened Early?
• Screening for Diabetes and Pre-Diabetes in The Postpartum Period
• What Are Glucose Target Levels?
• Diet and Exercise
• Pharmacologic Treatment
• Fetal Monitoring
• When to Deliver?

Screening for GDM – First or Second Trimester?

• ACOG supports the ‘2 step’ approach (24 to 28 week 1 hour venous glucose measurement following 50g oral glucose solution), followed by a 100g 3 hour oral glucose tolerance test (OGTT) if positive
  • Note: Diagnosis of GDM is based on 2 abnormal values on the 3 hour OGTT
    • ACOG recommends that currently there is insufficient evidence to diagnose GDM based on only one abnormal value
    • Patients with only one elevated value may require additional surveillance
• ACOG does not recommend routine screening for GDM <24 weeks 
• The USPSTF
  • Recommends screening for gestational diabetes in asymptomatic pregnant persons at ≥24 weeks of gestation or after (B recommendation)
  • Current evidence is insufficient to assess the balance of benefits and harms of screening for gestational diabetes in asymptomatic pregnant persons <24 weeks of gestation (I statement)
• ACOG suggests use of Carpenter and  Coustan vs national Diabetes Data Group (NDDG) criteria due to higher thresholds with NDDG and possibility of missing patients who would benefit from GDM diagnosis
  • Fasting blood sugar: <95 mg/dL (5.3 mmol/L)
  • 1 hour blood sugar: <180 mg/dL (10.0 mmol/L)
  • 2 hour blood sugar: <155 mg/dL (8.6 mmol/L)
  • 3 hour blood sugar: <140 mg/dL (7.8 mmol/L) 

Note: ACOG does state that some practices may use the ‘one step’ 75g OGTT vs ‘2 step’ “if appropriate for the population they serve” 

Who Should be Screened Early?

Consider early screening in pregnancy if patient is overweight with BMI of 25 (23 in Asian Americans), and one or more of the following

• Physical inactivity
• Family history of diabetes – 1st degree relative (parent or sibling)
• Black, Hispanic, Native American, Asian American, or Pacific Islander
• Previous pregnancy history of
  • GDM
  • Macrosomia (≥ 4000 g)
• Hypertension (140/90 mm Hg or being treated for hypertension) 
• HDL cholesterol ≤ 35 mg/dl (0.90 mmol/L)
• Fasting triglyceride ≥ 250 mg/dL (2.82 mmol/L)
• PCOS
• Conditions associated with insulin resistance (e.g., acanthosis nigricans, morbid obesity)
• Hgb A1C ≥ 5.7%, impaired glucose tolerance or impaired fasting glucose | If A1C>6.5%, diagnosis of pregestational diabetes is met and GCT/GTT not needed
• Cardiovascular disease
• HIV
• 35 years or older 
• Other factors suggestive of increased risk for pregestational diabetes

Screening for Diabetes and Pre-Diabetes in the Postpartum Period

4 to 12 weeks Postpartum 

• ACOG now suggests screening women who had GDM between 4 and 12 weeks postpartum for Diabetes and Pre-Diabetes
  • Note: This is a change from previous guidance that recommended 6 to 12 weeks

Immediately Postpartum

• Screening with the 75-g OGTT for type 2 diabetes during the delivery hospitalization “is a reasonable alternative in lieu of performing the 75-g OGTT at 4–12 weeks postpartum and may increase the rate of postpartum testing”

What Are Glucose Target Levels?

• ACOG recommends the following target levels to reduce risk of macrosomia
  • Fasting or preprandial blood glucose values < 95 mg/dL
  • Postprandial blood glucose values < 140 mg/dL at 1 hour and < 120 mg/dL at 2 hours
• Review weekly but may alter based on degree of glucose control

Diet and Exercise

• Nutritional assessment and plan
  • Counseling by registered dietician/nutritional team if available
  • Recommend complex carbohydrates, 3 meals and 2 snacks to limit glucose fluctuations
    • Ideal caloric distribution between carbohydrates, fat and protein not yet known
• 30 minutes of moderate-intensity aerobic exercise at least 5 days a week or minimum 150 minutes per week
  • Improvement seen with walking 10 to 15 minutes after each meal
• Monitor glucose levels after beginning dietary recommendations to confirm glycemic control

Pharmacologic Treatment

• ACOG recommends that insulin be the preferred therapy if glycemic control is not obtained with nonpharmacologic treatment
• Substantial number of patients started on oral therapy will require insulin during pregnancy
  • Starting insulin dose 0.7 to 1.0 units/kg daily
  • Dosage should be divided and long-acting or intermediate-acting insulin in combination with short-acting insulin should be used
  • Individualize based on patients glycemic pattern
  • Short acting analogues (e.g. insulin lispro and aspart) preferred over regular insulin due to more rapid onset
  • NPH insulin still used for but insulin glargine and detemir available for long-acting coverage
• If a patient cannot take insulin or declines, metformin can be used
  • Counsel about metformin risks including placental cross over and no long term studies in offspring available
    • May be associated with preterm birth
  • Starting dose: 500 mg nightly for 1 week, increase to 500 twice daily
    • Check baseline creatinine
  • Adverse events include abdominal pain and diarrhea – recommend with meals
  • Maximal dose is 2,500 to 3,000 mg per day, in two or three divided doses
• Glyburide should not be used in place of insulin as studies show worse outcome, including macrosomia and birth injury
  • Starting dose is 2.5 to 20 mg per day in divided doses
  • Up to 30 mg may be necessary to obtain glycemic control
  • Long term outcome studies also still lacking, although no short term adverse events have been noted

Fetal Monitoring

• On medication (A2GDM) with poor control and without co-morbidities: 32 weeks
  • Begin earlier if other co-morbidities are present
  • Fetal assessment for A2GDM in general is usually recommended based on the understanding that there may have been poor control at some point during the pregnancy
• Well controlled on diet (A1GDM): no consensus due to lack of data demonstrating stillbirth risk
  • Fetal assessment may not be necessary
  • If performed
    • Usually begun later than A2GDM and can be based on local practice
    • Include amniotic fluid volume assessment due to risk of polyhydramios

When to Deliver?

• Controlled on diet: 39w0d to 40w6d
  • Expectant management up to 40w6d appropriate with antepartum testing
• Well controlled on medication: Deliver at 39w0d to 39w6d 
• Poorly controlled: Individualize | Expert guidance supports earlier delivery but data lacking regarding precise timing
  • Delivery between 37w0d and 38w6d may be justified
  • Delivery between 34w0d and 36w6d weeks 0 days reserved for (1) failure of in-hospital glycemic control or (2) abnormal fetal testing
• Estimated fetal weight ≥4500: Counsel regarding risks and benefits of a scheduled cesarean section

Learn More – Primary Sources:

ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus

ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum

SOGC: Guideline No. 393-Diabetes in Pregnancy

USPSTF: Screening for Gestational Diabetes

The ObG Project is in no way affiliated with any outside entity or professional organization

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Gestational Diabetes Mellitus – Definitions, Risk Factors and Complications

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