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Medical Disorders and Pregnancy

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Medical Nutrition Management of Gestational Diabetes

Sharon B. Tilbe, MA, RD, LDN, CDE
Joslin Diabetic Center affiliate at Mercy Medical Center

(Please refer to the article "Diabetes in Pregnancy" by Catherine Hegarty, MD, for specific description of the condition, including incidence, causes and risk factors, signs and symptoms, diagnosis and insulin treatment.)

A cornerstone of blood glucose management of GDM is Medical Nutrition Therapy (MNT). The goal of MNT is to help the woman achieve normoglycemia without ketosis and optimal nutritional intake for maternal health and fetal growth. An estimated 50-75% of pregnancies complicated by GDM can be successfully managed with MNT alone. It is important to initiate such intervention as soon as possible after diagnosis. Referral to a Registered Dietitian (RD) should be made within 48 hours of diagnosis so that intervention can be initiated within one week after diagnosis.

The importance of the individualized nutrition assessment:
An individualized nutrition assessment is crucial to allow an accurate appraisal of the woman's nutritional status. This assessment includes defining her Body Mass Index or percentage of desirable pregravid body weight and optimal pattern of weight gain. The usual intake of protein, folic acid, calcium, and iron are determined, and since requirements of these nutrients are increased during pregnancy, adequacy of supplementation is assessed. Intake of fat, sodium, caffeine, artificial sweeteners and alcohol needs to be examined as they may be consumed in excess. The RD also reviews exercise/activity pattern, work schedule, ethnic and cultural food preferences.

Open-ended questions can identify specific problems affecting the food intake of the patient. The areas to question include but are not limited to; smoking behavior, nausea and vomiting, heartburn, diarrhea, constipation, aversions, cravings, special dietary requirements (i.e., lactose intolerance, celiac disease), money available for food purchase, frequency and location of dining out. These factors affect food intake and, thus, nutritional status. To maximize the use of visit time, it is helpful to have the patient bring in a three-day food intake diary to the first appointment with the RD. Once the RD has a clear picture of the woman's requirements, habits and preferences, the meal/food plan can be developed.

Calories and Weight Gain:
There are various documented opinions regarding the recommended calorie levels for women with GDM, particularly obese women. The following calorie recommendations are often used. Individualization is important, and adjustments will be made based on weight change patterns.

Weight Status

Recommended Caloric Intake If pregravid weight is:

Recommended Weight Gain

Within desirable range

30 Kcal/Kg/day/ present weight

25-30 lbs./11-16 kg.

120-150% desirable range

24 kcal/kg/day current weight

15-lbs./7 kg.

>150% desirable range

12-18 kcal/kg/day present weight

15 lbs./7kg

<90% desirable range

36-40 kcal/kg/day
or 30-kcal/kg present weight

28-35 lbs./13-21 kg.

Since GDM is most often detected in the latter trimester of pregnancy, it is possible that the overweight or obese patient will gain at least the recommended amount of weight by the time MNT is initiated. At that time, calories should not be severely restricted to foster weight loss, as weight loss efforts are best addressed during the postpartum period. Moderate calorie restriction, (no less than 1800 calories), for obese women with GDM has been proposed to help decrease postprandial blood glucose without ketonuria. This topic is among controversies mentioned below.

The meal plan and monitoring:
Once the nutrition assessment is complete, the RD and woman together develop a meal plan, which reflects treatment goals and factors of the woman's lifestyle. The recommended composition of the diet is ~40% calories from carbohydrate, 20% from protein, 40% from fat. The distribution of calories, particularly carbohydrate, makes a difference in the postprandial blood sugars. Although total carbohydrate intake is controlled and monitored, carbohydrate foods with a lower glycemic index are emphasized as preferable choices as they make a lesser impact on postprandial blood sugars. Soluble fibers found in legumes, fruits and vegetables tend to cause a slower rate of absorption of glucose. Insoluble fibers are not totally digested and speed the movement of food through the gastrointestinal tract. Some simple sugars can be included in the meal plan but should be used with caution. The RD will help the woman choose lower fat, high nutrient density foods, as needed. Recommendations for calorie and carbohydrate distribution vary somewhat, but a general guideline is:

Breakfast - 10-15% of total calories. *Limit carbohydrate initially to 15-45 Grams.
1 Snack - 5-10% of total calories. *
Lunch - 20-30 % of total calories
2 Snack - 5-10% of total calories. *
Supper - 30-40 %
3 Snack 5-10 % of total calories. *

*Protein added to early low-carbohydrate breakfast and snacks is helpful in reducing hunger.

Morning carbohydrate intake needs to be controlled, because, insulin resistance is greatest at that time due to larger maternal supply of cortisol. Including snacks between mealtimes helps to prevent hunger, helps reach recommended calories levels and reduces mealtime carbohydrate load. Smaller frequent feedings can help improve nausea, vomiting, heartburn, and postprandial blood glucose level and urine ketones. Ketonuria in pregnancy is usually caused by low carbohydrate intake, low calorie intake, or skipped meals or a lapse of more than ten hours between the last eating episode of the day and breakfast. Since women who are highly motivated to keep blood sugars within target range might shortchange themselves in calories or carbohydrates, it is recommended that they check their morning ketones to assure that they eating enough. The RD employs a variety of teaching methods and tools to achieve adherence to the meal plan. These include but are not limited to; carbohydrate counting, exchange meal plans, and use of Food Guide Pyramids. Sample menus usually prove to be helpful to the woman.

The effectiveness of the meal plan and the level of insulin resistance are monitored by the woman who checks her blood glucose at least four times daily with a glucometer. Fasting blood sugar below 90-95 mg/dl, and 1-hour postprandial less than 140 mg/dl, or 2-hour postprandial less than 120 mg/dl are generally accepted targets. Urine ketone checking helps to signal inadequate calorie/carbohydrate intake, or need for more frequent feedings. Adherence to the regime of following the meal plan and monitoring is the responsibility of the pregnant woman. Motivation for adherence the treatment plan emerges when the woman understands the importance of controlling blood sugars while allowing fetal growth.

Follow-up care:
At the first visit with the RD, MNT is initiated. Discussions at follow-up visits determine if the patient is achieving desired outcomes and utilizing self-monitoring tools. Records of monitoring blood glucose and urine ketones are reviewed, and weight is checked. If outcomes are not achieved because the meal plan is not being followed, or if tools for self-monitoring are not are properly used, the clinician needs to assess what the barriers to adherence might be. At times, a woman may adhere to the proposed regimen, but the desired outcomes are not achieved. In these cases, The RD will employ intervention strategies by altering the meal plan, or activity pattern. Insulin therapy may be needed. If the patient is achieving desired outcomes and utilizing available monitoring tools, the follow-up visits serve to provide further education and support.

Throughout the duration of the pregnancy, frequent follow-up visits with the RD enable the clinician to identify effectiveness of, and the woman's adherence to the treatment plan. If regular and frequent scheduled follow-up visits are truly not feasible, communication between the clinician and woman by review of blood glucose records and telephone visits can be occasionally substituted.

Artificial sweeteners, sodium and caffeine:
It is advisable to avoid saccharin during pregnancy as it crosses the placenta. Aspartame (contraindicated with phenalketonuria), acesulfame-K and sucralose are allowed in limited amounts. Artificial sweeteners containing carbohydrate need to be counted as part of total carbohydrate. Sodium is not routinely restricted during pregnancy. Caffeine is allowed in moderation. Less than 300 mg/day of caffeine is allowed to limit potential harm to the fetus.

Pre-existing Diabetes and Pregnancy: meal plan issues:
Many of the same dietary strategies are employed in constructing a meal plan for the pregnant woman who has pre-existing diabetes. Currently, the FDA does not approve oral agents for blood sugar control. Therefore, insulin therapy is used for both Type 1 and Type 2 diabetes during pregnancy. In developing a meal plan for the pregnant woman who has pre-existing diabetes, the carbohydrate and insulin must be matched to prevent hypoglycemia and to meet target blood glucose goals. A plan of three meals and three snacks is often used, initially. If blood sugar targets are not being attained, the meal plan will be altered during follow-up visits. Lifestyle and exercise/activity patterns need to be considered when planning the timing of meals and snacks to prevent hypoglycemia.

Hypoglycemia must be avoided. Three meals and three regular snacks are proven to be helpful in circumventing this complication of insulin therapy.

Medical Nutrition Therapy is a cornerstone of treatment for GDM and is an important part of treatment for pre-existing diabetes complicated by pregnancy. The individualized meal plan is designed to meet the woman's physiological requirements, yet takes into account her personal requirements of lifestyle and abilities. Blood glucose records guide the RD to make appropriate adjustment in the meal plan. The goals of MNT are to achieve; normoglycemia with no ketosis, desirable weight gain, optimal nutritional intake and avoidance of nutrition related complications.

Controversies in Medical Nutrition Therapy for GDM and Diabetes complicated by pregnancy:
Researchers continue to disagree on some treatments for GDM and Diabetes complicated by pregnancy. Lacking substantial clinically based evidence, health care providers differ in their recommendations for patients. Some controversies include:

  1. Should calories be restricted for overweight and obese women with GDM?
  2. Exercise for GDM and Type 2 diabetes complicated by pregnancy is beneficial to overcome insulin resistance. Do the benefits outweigh the risks?
  3. Can artificial sweeteners be safely used during pregnancy?


  1. Nutrition Practice Guidelines for Gestational Diabetes Mellitus Diabetes Care and Education and Women and Reproductive Nutrition Practice Groups of the American Dietetic Association, 2001
  2. Diabetes Care, Volume 25, Supplement 1, pp. 167-169. "Medical Nutrition Therapy for Special Populations"
  3. American Diabetes Association: Clinical Practice Recommendations 2002
  4. Medical Management of Pregnancy Complicated by Diabetes, third edition The American Diabetes Association Inc. Clinical Education Series 2000
  5. Up-To-Date® Online 10.2 'Medical management of type 1 and type 2 diabetes mellitus during pregnancy'
  6. Up-To-Date® Online 10.2 'Treatment and course of gestational diabetes mellitus'
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