Management of Gestational Diabetes

There are no universal guidelines in the management of GDM. A recent Australian randomized, controlled trial of 1,000 women with gestational diabetes showed that treating women with GDM reduced the risk of perinatal complications [60]. In this study by Crowther et al., the intervention group received MNT, self-monitored their blood glucose levels, and if indicated received insulin therapy. Perinatal complications were 1% in the intervention group and 4% in the group receiving routine care.

10.11.5.1 Medical Nutrition Therapy

MNT is the cornerstone of treatment in the management of GDM. The American Diabetes Association and the American College of Obstetricians and Gynecologists recommend nutritional counseling by a registered dietitian and an individualized meal plan [3, 58]. The American Dietetic Association's evidence-based Nutrition Practice Guidelines have identified the following MNT goals for GDM: (1) to achieve and main-

Table 10.5

Diagnostic Criteria for Gestational Diabetes Mellitus

100 g OGTT

75 g OGTT

Fasting

95 mg/dl (5.2 mmol/l) 180 mg/dl (10 mmol/l) 155 mg/dl (8.6 mmol/l) 140 mg/dl (8.1 mmol/l)

95 mg/dl (5.2 mmol/l) 180 mg/dl (10 mmol/l) 155 mg/dl (8.6 mmol/l)

From [12], OGTT: Oral Glucose Tolerance Test tain normoglycemia, (2) to provide sufficient calories to promote appropriate weight gain and avoid maternal ketosis, and (3) to provide adequate nutrients for maternal and fetal health [61]. The American Dietetic Association provides an algorithm for MNT for GDM (Fig. 10.1). The Institute of Medicine's recommendations are used to determine the appropriate weight gain for women with gestational diabetes (38). The EER are the same for pregnant women without diabetes. Monitoring weight gain, and reviewing blood glucose, food and if necessary, ketone records are other useful tools to determine diet adequacy.

The Dietary Reference Intakes do not provide a recommendation EER for obese women. Several studies used various calorie restrictions to determine minimum energy requirements, while avoiding ketonuria and ketonemia. A minimum of 1,700-1,800 kcal/ day appears to improve glucose control without increasing ketone levels [3, 58, 61].

Referral to Dietitian

Made within 48 hours of diagnosis for self-management education and nutrition therapy

Initial visit within 1 week of referral:

Assessment

Medical Nutrition Therapy Exercise

Self-Management Education Tools:

a. appropriate food plan for patient b. daily food records c. SMBG records d. ketone testing if needed Insulin if needed

First follow-up within 1 week *Documentation/Communication

Follow-Up Visit

Evaluate patient outcomes

Is patient achieving clinical outcomes and is patient using self-management techniques correctly?

Clinical Outcomes of MNT:

Blood Glucose Goals:

Whole Blood Plasma mg/dL

2 hr PP: <120 <130

  • achieve and maintain normoglycemia
  • consume adequate calories to promote appropriate gestational weight gain and avoid maternal ketosis
  • consume food providing nutrients necessary for maternal and fetal health
  • decrease nutrition related complications
  • Documentation/Communication
  • to referral source
  • summarize assessment
  • specify therapy plan and recommendations
  • specify follow-up plan

Is patient achieving clinical outcomes and is patient using self-management techniques correctly?

Provide support, answer questions a. Adjust food/exercise plan to individual Needs b. Continue/review self-management Education c. Adjust testing regimen if appropriate *Documentation/Communication

  • Evaluate cause(s) that prevent achieving clinical outcome
  • Determine barriers that may prevent implementing therapy
  • Provide intervention:

a. adjust food/exercise plan b. continue/review self-management education c. determine need for insulin therapy/make referral *Documentation/Communication

Determine Follow-Up Plan

Birth

Postpartum visit

Determine Follow-Up Plan

Follow-up Visit Schedule

If patient needs insulin make referral immediately

  • Second visit within 1 week
  • Third visit 1-3 weeks
  • Subsequent follow-up 2-3 weeks until birth

Fig. 10.1. Algorithm for MNT. (From [61], used with permission)

Carbohydrates are the main contributors of postprandial glucose excursions in GDM. The amount, source, and distribution of carbohydrates are determined in conjunction with blood glucose monitoring. The nutrition practice guidelines recommend restricting the carbohydrate content to 40-45% of total calories, but not less than the Dietary Reference Intakes recommendation of 175 g/day to achieve blood glucose goals. Carbohydrate sources include whole grains, dried beans and peas, and lentils, which are more nutrient dense and have a lower glycemic response than processed foods, such as instant products (e.g., cereals, rice, and potatoes) or highly refined grain products.

The distribution of carbohydrates into three meals and two to four snacks will help control postmeal blood glucose levels [61]. Carbohydrate intake is more restricted at breakfast than at other meals, as hormonal levels are higher in the morning. The total amount of carbohydrates at breakfast can range from 15 to 45 g. Breakfast cereals, milk, and fruit may need to be consumed at other meals or snacks. Carbohydrate distribution at lunch and dinner is usually 30-45 g or higher, depending on postprandial glycemic levels. The distribution of snacks is 15-45 g, with a smaller snack in the morning. An evening snack will help avoid overnight starvation ketosis.

Protein is not associated with postprandial glycemic elevations. The protein intake increases to 25-25% of total calories as the carbohydrate level is reduced, and usually exceeds the Dietary Reference Intakes of 71 g/day or 1.1 g/kg/day [61]. Fat makes up 35-40% of the total calories, with the majority as monosaturated and polyunsaturated fats [62, 63].

10.11.5.2 Self-Management Tools

Self-management is important for improving perinatal outcome in GDM. Other self-management tools in addition to MNT include self-monitoring of blood glucose and ketone levels, physical activity, and the initiation of medication, when necessary.

  1. 11.5.2.1 Self-Monitoring of Blood Glucose. Although the American Diabetes Association and the American College of Obstetricians and Gynecologists recommend daily monitoring of blood glucose levels in GDM, there is no consensus on frequency of testing [3, 58]. Research has indicated fewer complications (macrosomia, cesarean section, birth injury, neonatal hypoglycemia) with daily use of blood glucose meters than with weekly laboratory testing of fasting and postprandial levels [3]. While preprandial testing is recommended with preexisting diabetes, postprandial monitoring of blood glucose levels have yielded better outcomes, e.g., decrease in fetal macrosomia, large-for-gestational-age infants, in GDM [64]. Optimal testing times for blood glucose levels have not been established. Studies comparing 1-h and 2-h postprandial monitoring have shown conflicting results [65, 66]. (See Table 10.4 for target blood glucose levels.)
  2. 11.5.2.2 Ketone Monitoring. In an effort to avoid insulin injections, women may consume fewer calories than recommended; however, this practice may increase their risk of developing ketones. Rizzo et al. found decreased intelligence scores correlated with ketonemia [67]. Urine ketone monitoring is not widely used in practice because it does not reflect the level of ketonemia, but it may be useful in detecting inadequate calorie or carbohydrate intake [3, 61].
  3. 11.5.2.3 Physical Activity. Physical activity may have a positive effect on glycemic control by increasing insulin sensitivity and obviating the need for insulin therapy [58, 68, 69]. Low-impact aerobics, such as walking, stair climbing, or swimming are acceptable. The activity should be performed after meals to improve glycemic levels. Pregnant women with diabetes should seek medical approval prior to beginning an exercise program.
  4. 11.5.2.4 Medication. Insulin therapy is used concurrently with MNT if normogly-cemia is not consistently maintained with diet only. There is no consensus of opinion as to when insulin therapy should be instituted. The nutrition practice guidelines recommend beginning insulin therapy 2 weeks after MNT is implemented [61]. The American Diabetes Association and the American College of Obstetricians and Gynecologists use different glycemic cut-offs for initiating insulin (Table 10.6). Ultrasound measurement of the fetal abdominal circumference to determine macrosomic growth is also used to determine initiatiation of insulin therapy [70].

Human-based insulin is preferred over animal-based because it is less allergenic. The type, dosage, and regimen vary but are usually a combination of short-acting and intermediate-acting insulin. Calculation of the starting dose uses an approach that is similar to that employed for preexisting diabetes, and self-monitoring of blood glucose is used to guide the dose and timing of the regimen and subsequent adjustments. Insulin analogs are not yet approved by the Food and Drug Administration for use in GDM. Studies using insulin Lispro and insulin Aspart in GDM were not associated with adverse effects [71, 72].

Prior to 2000, oral antidiabetic agents were contraindicated during pregnancy. Firstgeneration sulfonylureas crossed the placenta and were thought to cause fetal hyper-insulinemia or teratogenicity. A randomized trial by Langer et al. in which Glyburide, a second-generation sulfonylurea, was compared to insulin and reported no difference in the incidence of maternal or fetal complications, including preeclampsia, cesarean sections, macrosomia, or fetal anomalies [73]. Glyburide was also not detected in the cord serum. Four percent of the women on Glyburide did require insulin therapy. The American Diabetes Association and the American College of Obstetricians and Gynecologists have not recommended Glyburide in pregnancy, although both organizations have acknowledged its use in controlling blood glucose levels in GDM. The advantages of Glyburide in pregnancy, according to healthcare providers who advocate its use, are that it is cost-effective, non-invasive, and may result in better compliance than insulin injections [74]. Recent research in Glyburide therapy use in pregnancy demonstrated a failure rate of 12-20% [75, 76]. Women with high fasting blood glucose levels (>110 mg/dl) were more likely to be switched to insulin therapy [76]. Further research is needed to determine the safety of other oral antidiabetic agents in pregnancy.

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