II. Indications: Gestational Diabetes

III. Monitoring: Blood Glucose

  1. Standard Glucose monitor is preferred over Continuous Glucose Monitors
    1. Continuous Glucose Monitors have limited evidence for Gestational Diabetes in 2022
  2. Frequency of Blood Glucose Monitoring
    1. Insulin therapy
      1. Blood Sugar Monitoring 4 times daily
    2. Diet control
      1. If well controlled, obtain Blood Sugars 4 times on 2 days per week OR twice daily
      2. Increase monitoring to four times daily if 2 values/week abnormal
  3. Target Levels
    1. Before Breakfast or early morning (2-6 am): 60 to 95 mg/dl
    2. Before Lunch,Dinner: 60 to 115 mg/dl
    3. One hour post prandial goal: under 140 mg/dl
    4. Two hour post prandial goal: under 120 mg/dl
    5. Check Urine Ketones in early morning
  4. Preferred monitoring: Postprandial Blood Glucose
    1. Post-prandial Blood Glucose Monitoring preferred
    2. Associated with improved outcomes
      1. Lower Hemoglobin A1C levels
      2. Lower birth weights
      3. Fewer Cesarean Sections
    3. References
      1. De Veciana (1995) N Engl J Med 333:1237-41 [PubMed]

IV. Evaluation: Initial

V. Management: Diet controlled management

  1. Indications
    1. Blood Sugars within target range (see above)
  2. Monitoring
    1. See Blood Glucose Monitoring above
  3. Dietary recommendations
    1. Refer to registered dietician
    2. Restrict Carbohydrates to <33 to 40% of daily calories
    3. Some studies have recommended a low Glycemic Index diet
      1. However maintain at least 175 g complex Carbohydrates daily
    4. Caloric restriction if BMI > 30 kg/m2
      1. Limit to 25 KCal/kg of actual weight per day
      2. Weight Gain in Pregnancy >40 pounds (18 kg) is associated with Fetal Macrosomia in 40% of cases
        1. Black (2013) Diabetes Care 36(1): 56-62 [PubMed]
      3. Avoid severe caloric restriction
        1. Ketonemia associated with psychomotor delay
        2. Rizzo (1995) Am J Obstet Gynecol 173:1753-8 [PubMed]
  4. Exercise recommendations
    1. Regular aerobic Exercise improves glycemic control
    2. Circuit Resistance Training improves glycemic control
      1. Brankston (2004) Am J Obstet 190:188-93 [PubMed]

VI. Management: Oral Hypoglycemics

  1. Indications: Failed diet control (see above)
    1. More than 50% of Glucose values in a week are above goal (see above) OR
    2. More than 2 Glucose values >10 mg/dl above goal at the same meal in a 2 week period
  2. Precautions
    1. Oral agents are first-line Gestational Diabetes agents
      1. Followed experimental use in 2005-2010 to confirm safety, efficacy
    2. Metformin is not FDA approved in pregnancy
      1. However, it is pregnancy category B
    3. Metformin crosses the placenta
      1. However, it is not associated with birth defects or short term adverse neonatal outcomes
      2. Metformin is the only Oral Hypoglycemic that appears safe in pregnancy
    4. Sulfonylureas are not recommended in pregnancy
      1. Of the Sulfonylureas, only Glyburide is a pregnancy category B
      2. Glyburide was initally thought the only safe Sulfonylurea in pregnancy
        1. Jacobson (2005) Am J Obstet Gynecol 193(1): 118-24 [PubMed]
      3. As of 2015, Glyburide is no longer recommended in pregnancy as of 2015
        1. Greater risk of Neonatal Hypoglycemia and macrosomia (compared with Insulin)
        2. Balsells (2015) BMJ 350:h102 [PubMed]
    5. Insulin is FDA approved in pregnancy and has a longer track record
      1. Up to 30 to 40% of women started on Oral Hypoglycemics require transition to Insulin in pregnancy
  3. Management
    1. Continue lifestyle management as above for diet controlled Diabetes Mellitus management
    2. Review Glucose monitoring log every 2 weeks
    3. Metformin
      1. Start at 500 mg once daily with food and titrate to a maximum of 2500 mg daily
      2. Metformin has also been used in Metabolic Syndrome and PCOS to facilitate conception (effective in 42% of cases)
        1. If patient conceives on Metformin, continue for first 20 weeks (prevents Rebound Hyperglycemia)
  4. References
    1. Rowan (2008) N Engl J Med 358(19):2003-15 [PubMed]
    2. Glueck (2002) Hum Reprod 17:2858-64 [PubMed]
    3. Greene (2000) N Engl J Med 343:1178-9 [PubMed]
    4. Langer (2000) N Engl J Med 343:1134-8 [PubMed]

VII. Management: Insulin

  1. Indications
    1. Preexisting Insulin Dependent Diabetes Mellitus
    2. Failed diet and Oral Hypoglycemic control (see above) with >20% abnormal Glucose values
      1. Fasting Blood Glucose > 95 mg/dl OR
      2. One hour postprandial >140 mg/dl OR
      3. Two hour postprandial Blood Glucose >120 mg/dl
  2. Protocol
    1. See Insulin Management in Pregnancy
    2. See Insulin Management in Labor
    3. Endocrine consult as needed for Insulin Dosing

VIII. Monitoring: Antepartum aggressive monitoring for complications

  1. Aggressive monitoring is not needed for diet controlled Gestational Diabetes (no medications)
    1. No increased risk of Stillbirth
    2. Loomis (2006) J Fam Pract 55(3): 238-40 [PubMed]
    3. Mitanchez (2010) Diabetes Metab 36(6 pt 2): 617-27 [PubMed]
  2. Monitoring as directed by local established protocols
  3. Monitoring starting at 32 weeks gestation
    1. Weekly Non-Stress Test (biweekly if on Insulin or poor control)
    2. Amniotic fluid index weekly if on Insulin or poor control
    3. Some protocols include Biophysical Profile
  4. Daily Fetal Kick Counts starting at 34 weeks gestation
  5. Obstetric Ultrasound monthly (not universally recommended)
    1. Assess Fetal Growth for macrosomia
    2. Not universally adopted as Ultrasound may unnecessarily increase the cesarean delivery rate
      1. Little (2012) Am J Obstet Gynecol 207(4): 309.e1-309.36 +PMID:22902073 [PubMed]
  6. Consider fetal Echocardiography at 18 to 22 weeks gestation in early onset Gestational Diabetes Mellitus
    1. Increased risk of fetal cardiac defects
    2. (2020) J Ultrasound Med 39(1): E5-16 [PubMed]
  7. Prenatal Visit frequency and monitoring based on Blood Sugar control
  8. Plan Labor Induction by 39-40 weeks

IX. Management: Intrapartum

  1. See Insulin Management in Labor
  2. Timing of delivery is typically at 39 to 40 weeks
    1. Consider offering Cesarean Section for EFW > 4500 g (9 lb 14 oz)
      1. However, Ultrasound biometry predicted fetal weight has poor Test Sensitivity
    2. Delivery prior to 39 to 40 weeks not indicated unless
      1. Poor glycemic control
      2. Other fetal or maternal complications

X. Management: Postpartum Care

  1. Postpartum Glucose Screening
    1. Hemoglobin A1C at >=13 weeks postpartum
      1. Hemoglobin A1C>6.5% consistent with Diabetes Mellitus (>5.7% Impaired Glucose Tolerance)
    2. Glucose Tolerance Test 2 hour (75 g Glucola)
      1. Non-Lactating: Schedule at 6-12 weeks
      2. Breast Feeding: Schedule at 6 months
      3. Abnormal in up to 36% of post-partum women
        1. Diabetes Mellitus if Fasting Glucose >125 mg/dl OR 2 hour Glucose >199 mg/dl
        2. Impaired Fasting Glucose if Fasting Glucose >100 mg/dl OR 2 hour Glucose >140 mg/dl
  2. Management
    1. Normal Postpartum Glucose Screening
      1. Repeat Hemoglobin A1C or Fasting Blood Glucose every 1-3 years
      2. Risk of developing Type II Diabetes Mellitus within 10 years (GDM high risk groups): 50%
    2. Impaired Glucose Tolerance
      1. See Nutrition in Diabetes Mellitus Type 2
      2. Lifestyle modification (e.g. weight loss, dietary changes)
      3. Consider nutrition referral
      4. Consider Metformin
      5. Annual repeat testing for Diabetes Mellitus
    3. Diabetes Mellitus
      1. Confirm results
      2. See Type II Diabetes Mellitus
      3. See Type II Diabetes Medications
  3. Prevention
    1. Maintain Ideal Body Weight
    2. Moderate intensity Exercise for 150 minutes per week

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