Diabetes Outreach Network
QUICK REFERENCE GUIDE TO DIABETES FOR HEALTH CARE PROVIDERS

Chapter 12
Gestational Diabetes Mellitus (GDM)

Risk assessment should be identified at the first prenatal visit. Women who meet all of the following criteria are considered low risk: under the age of 25, are of normal weight, have no family history of diabetes, have no history of abnormal glucose tolerance, have no history of poor obstetric outcome, and not members of a high risk ethnic group. No screening is required for those at low risk of developing GDM.

Women who are at high risk of developing diabetes (marked obesity, prenatal history of GDM, glycosuria, strong family history of diabetes) should be tested immediately, and retested at 24-28 weeks, if necessary. All others should be screened at 24-28 weeks of pregnancy.

Diagnostic Tests

Random 50 gram, 1 hour glucose challenge

• Glucose >200 mg/dl, diagnosis of gestational diabetes is made.
• If >140 mg/dl: administer 100 gram glucose, 3 hour oral glucose tolerance test (3 days unrestricted carbohydrate diet of at least 150 grams per day, followed by 8-14 hour overnight fast).

Three hour, 100 gram glucose oral glucose tolerance test (after an 8-14 hour fast)

• Diagnosis of gestational diabetes is made when 2 or more values from this test are:
  • > 95 mg/dl at fasting
  • > 180 mg/dl at 1 hour
  • > 155 mg/dl at 2 hours
  • > 140 mg/dl at 3 hours
• If only 1 out of 3 values is abnormal, retest at 32 weeks.

Nutritional Intervention
All women should meet with a registered dietitian for assistance with meal planning, with calories sufficient for adequate weight gain. Carbohydrates should be based on the effect on the blood glucose and spaced throughout the day into 3 meals and 2-4 snacks. Carbohydrates can be limited to 35-40% of total calories, and are generally less well tolerated in the morning. A moderate restriction of no more than 30-45 grams at breakfast is usually recommended, with monitoring of blood glucose response. Non-nutritive sweeteners are generally safe in pregnancy. Supplementation with folic acid (400 ug per day) is recommended for all women before and during pregnancy.

Monitoring

• Weight gain (usually about 1-2 pounds per week for the second and third trimesters). Recommend at least 15 pounds for the obese, and up to 40 pounds for the underweight.
• AM urine ketones - if present, may need additional carbohydrate calories before bed or may need shorter period to time between evening snack and breakfast.
• Food intake and blood glucose levels - fasting, before meals, and 1-2 hours after meals.

Meal plan is adjusted based on weight gain, AM ketones, and blood glucose levels.

Blood Glucose Goals (plasma values)

* American Diabetes Association
** American College of Obstetricians and Gynecologists

Insulin Administration
Generally started if nutritional therapy fails to keep blood glucose <105 mg/dl fasting or <130 mg/dl 2-hour postprandial.

Starting doses for gestational diabetes, in third trimester:

• 0.7 units/kg/day, give 2/3 in the morning as 2/3 NPH, 1/3 R (some use 70/30). Give the other 1/3 in the evening as 2/3 NPH and 1/3 R.
• Obese: 0.8-1 unit per kg per day in at least 2 doses per day
• Fasting hyperglycemia: may treat with HS dose of 10 units NPH

Oral hypoglycemic agents and insulin analogs are not approved for use in gestational diabetes at this time.

Activity and Pregnancy

• Activity may help with glycemic control.
• If active prior to pregnancy, a woman with gestational diabetes can usually continue being active.
• Heart rate should not exceed 140 beats per minute.
• Activities of less than 15-20 minutes may be indicated.
• Moderate, regular activity, especially after meals may have a positive impact on blood glucose levels.

Breast Feeding

• Should be strongly encouraged for as long as possible.
• May help with weight loss postpartum and reduce the risk of future diabetes.

Diabetes after Delivery

• Most women return to normal blood glucose following delivery.
• An estimated 40-60% of women with gestational diabetes eventually develop diabetes as they age
  • risk of developing diabetes can be minimized if women engage in regular physical activities and maintain desirable body weight.
• A 2 hour oral glucose tolerance test with 75 grams of glucose is recommended at the first 6-8 week postpartum visit.

References:American Diabetes Association (2006). Clinical Practice Recommendations. Diabetes Care, Vol 29 (1).

Jovanovic, L (Ed) (2000). Medical Management of Pregnancy Complication Diabetes, 3rd Ed. Alexandria, VA: American Diabetes Association.