Gestational Diabetes (Part 1)

What is Gestational Diabetes (GDM)?

  • Gestational diabetes is defined as any degree of glucose intolerance (with resultant hyperglycemia) that is first discovered during pregnancy.

How Common is Gestational Diabetes?

  • Diabetes is seen in approximately 6 to 7 percent of all pregnancies, of which, 90 percent are considered gestational diabetes.

Why Does Gestational Diabetes Occur?

  • The second and third trimester of pregnancy are characterized as a time of insulin resistance (this is due to certain pregnancy hormones that counteract insulin action). If the body cannot keep up with the increased insulin needs, then hyperglycemia will ensue.

Who is at Risk for Gestational Diabetes?

  • 25 years and older
  • Certain races/ethnicities: Asian, Pacific Islander, Native American, Hispanic and African American
  • Family history of diabetes
  • Overweight (BMI>25) or obese (BMI>30)
  • Previous pregnancy with birth weight of baby being 9 pounds or greater
  • History of random plasma glucose of 120 mg/dL or greater

Screening for Gestational Diabetes:

  • Done at 24-28 weeks (screening may also be done at first prenatal visit if woman is at high risk)
  • Two-Step Diagnosis:
    • Step 1:
      • Consume 50-gram glucose drink (non-fasting)
      • Plasma glucose is measured in 1 hour
      • If plasma glucose is greater than 140 mg/dL, Step 2 (100 gram oral glucose tolerance test) is completed
    • Step 2:
      • Consume 100-gram glucose drink (fasting)
      • Diagnosis of GDM is made when 2 or more plasma glucose levels meet or exceed:
        • Fasting: 95 mg/dL
        • 1 hour: 180 mg/dL
        • 2 hour: 155 mg/dL
        • 3 hour: 140 mg/dL

Potential Complications of Gestational Diabetes

  • Hypertension
  • Preeclampsia
  • Macrosomia (birth weight>8 pounds 13 ounces)
  • Cesarean section
  • Pelvic Trauma
  • Dystocia (one or both of infant’s shoulders becomes “stuck” behind the mother’s pelvic bone as the infant descends into the birth canal)
  • Increased risk of developing type 2 diabetes (blood glucose level is usually checked 6 to 12 weeks postpartum to screen for diabetes) and cardiovascular disease
  • Neonatal hypoglycemia
  • Infant born to mother with GDM may be at increased risk for: overweight/obese, type 2 diabetes and high cholesterol

Treatment of Gestational Diabetes:

  • The first line of treatment for GDM includes lifestyle modifications:
  • If blood glucose levels are not maintained within the recommended range, then medication is necessary.
    • Insulin is the preferred medication for treatment of uncontrolled gestational diabetes.
    • Metformin and Glyburide are two oral medications that may also be used for treatment of uncontrolled gestational diabetes. Both medications cross the placenta and although there have been no adverse effects on the fetus reported, there is a lack of long-term studies.

Blood Glucose Targets for Gestational Diabetes:

  • Fasting:
  • One- hour after a meal:
  • Two-hours after a meal:
  • It is generally recommended that blood sugar be checked up to 4 times per day (fasting and 1 to 2 hours after each meal)

A few last words...

  • As soon as you are diagnosed with GDM, ask your physician about meeting with a diabetes educator (CDE) and/or registered dietitian (RD) to learn more about management of GDM.
  • Stay tuned for Gestational Diabetes Part 2 to learn more about how GDM is managed with medical nutrition therapy.

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