Gestational diabetes mellitus (GDM) is a condition that develops during pregnancy, characterized by glucose intolerance with onset or first recognition during pregnancy. Managing GDM is crucial for both the short-term and long-term health of the mother and child, reducing the risk of birth complications, babies large for gestational age (LGA), and the development of type 2 diabetes in both. Lifestyle changes, particularly dietary adjustments, are essential in the management of GDM. This article provides an overview of recommended dietary interventions and components for women with GDM during pregnancy.
Understanding Gestational Diabetes
During pregnancy, women gradually develop insulin resistance, which ensures sufficient nutrient supply for the growing fetus. However, in women with GDM, this insulin resistance leads to hyperglycaemia. Glucose passes through the placenta to the fetus, increasing fetal insulin production, which in turn stimulates fetal growth, causing macrosomia and LGA. The prevalence of GDM is rising, increasing the need for effective treatment strategies.
First-line treatment in GDM includes medical nutrition therapy, weight management, and physical activity. Lifestyle modification alone is often sufficient to control blood glucose in a significant percentage of women diagnosed with GDM.
Weight Management During Pregnancy with GDM
Recommended Weight Gain
The recommended weight gain during pregnancy for women with GDM is the same as for women with normal glucose tolerance pregnancies (NGTP). Gestational weight gain (GWG) should support the growth and development of the fetus. Recommendations for GWG vary slightly by country but often align with those made by the Institute of Medicine (IOM) of National Academies.
To provide practical guidance, the following weight gain rates during the 2nd and 3rd trimesters are often recommended:
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- BMI less than 18.5 kg/m2: 0.44-0.58 kg/week
- BMI between 18.5 to 24.9 kg/m2: 0.35-0.50 kg/week
- BMI between 25.0 to 29.9 kg/m2: 0.23-0.33 kg/week
- BMI of 30 kg/m2 or above: 0.17-0.27 kg/week
Energy Requirements
There is no conclusive evidence suggesting that energy requirements for women with GDM should differ from those for normoglycemic women, nor is there a specific optimal calorie intake. However, additional assessment of daily energy requirements is based on trimesters, with varying recommendations.
Avoiding Excessive Weight Gain
Excessive weight gain in women with GDM has been linked to an increased risk of hypertensive disorders of pregnancy, caesarean section, and LGA-babies. Weight stabilization is the goal for women with GDM who have already achieved the recommended weight gain, and calorie restriction may be necessary. A calorie restriction of 30-33% has been shown to reduce hyperglycaemia and plasma triglyceride levels in women with obesity and GDM.
Carbohydrate Intake for Women with GDM
Carbohydrates are the most important macronutrient for women with GDM. The digestion and absorption of carbohydrates significantly impact blood glucose levels, with postprandial hyperglycaemia being primarily dependent on carbohydrate intake. Both the amount and type of carbohydrate affect glucose levels.
Glucose is the principal energy substrate for the placenta and fetus, essential for normal fetal growth and metabolism. The IOM recommends 46-65 Energy percent (E%) from carbohydrates and a minimum of 175 g of carbohydrate daily to ensure appropriate fetal growth and cerebral development and function. Ketonemia and/or ketonuria should be avoided, as it has been associated with lower mental or motor function in the offspring.
Carbohydrates should predominantly consist of starchy foods with a low glycaemic index and a naturally high content of dietary fiber, such as vegetables, legumes, fruits, and whole grains. The intake of added sugars should be minimized.
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Recommended Daily Carbohydrate Intake
There is no international consensus on the appropriate amount of daily carbohydrate intake for women with GDM. Some guidelines recommend that daily carbohydrate intake should not exceed 40-50E%. Other countries follow the general recommendation for NGTP, which is 45-60E% in the Nordic countries.
Clinical trials comparing low-carbohydrate diets with higher-carbohydrate diets have yielded conflicting results. Some studies suggest that lower carbohydrate diets result in lower postprandial glucose, while others show no significant differences in pregnancy outcomes. It is important to note that lower carbohydrate intake often leads to increased fat intake, which has been associated with increased serum fatty acids, insulin resistance, and increased fetal fat accretion in NGTP.
Simple vs. Complex Carbohydrates
Simple carbohydrates typically result in higher postprandial excursions than complex carbohydrates. The Nordic Nutrition Recommendations (NNR) recommend a minimum of 25 g dietary fiber for women in general, while the American Diabetes Association recommends a minimum of 28 g of fiber for women with GDM, similar to IOM recommendations for normoglycemic women during pregnancy. These recommendations can be met by consuming 600 g of fruit and vegetables a day, with a minimum of 300 g vegetables, focusing on rough and fibrous vegetables, and by choosing wholemeal bread, pasta, and rice.
Glycaemic Index (GI) and Glycaemic Load (GL)
Carbohydrate foods can be classified based on their effect on postprandial blood glucose, expressed as a percentage of the blood glucose response of a reference food. Foods with a GI >70 are considered high GI foods, while those with a GI ≤55 are considered low GI foods. Studies have shown that consuming a diet with a low GI can reduce the need for insulin in women with GDM.
Glycaemic load (GL) considers both the GI and the total available carbohydrate content in a given amount of food. Low GL diets have been shown to improve glycaemic control in type 2 diabetes, and the results might also apply to GDM. GL has been shown to be a more powerful predictor of postprandial glycaemia and insulinemia compared to carbohydrate content alone.
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Meal Timing and Distribution
It has been suggested that breakfast should only contain small amounts of slowly absorbed carbohydrates, as there is usually a higher postprandial increase in blood glucose in the morning. Some guidelines recommend a maximum of 30 g carbohydrate at breakfast. However, scientific evidence supporting these recommendations is limited. Some studies indicate that a higher carbohydrate intake in the morning may lead to lower mean glucose and fasting blood glucose. More randomized clinical trials are needed to determine the optimal carbohydrate intake in the morning for women with GDM.
Artificial Sweeteners
The intake of artificial sweeteners (AS) during pregnancy has been increasing. Regulatory bodies have reported certain AS, such as asulfame potassium, aspartame, saccharin, and steviol glycosides, to be safe for use during pregnancy. However, observational studies have raised some concerns, including increased infant BMI, childhood obesity, and a small increase in preterm birth. Further research, especially RCTs with longer follow-up times, is warranted.
Key Recommendations for Carbohydrate Intake
Carbohydrates have the greatest impact on postprandial hyperglycaemia. Despite some studies suggesting a beneficial effect of low-carbohydrate diets, there is currently no evidence to recommend a carbohydrate intake that is lower than in NGTP, and a minimum of 175 g of carbohydrate should be ensured. The exact amount of carbohydrate should be individualized, with a focus on the types of carbohydrate.
Practical Dietary Strategies for Managing GDM
The Diabetes Plate Method
The Diabetes Plate method is a simple and effective way to create balanced meals without the need for detailed counting or measuring. Using a 9-inch plate, fill half with non-starchy vegetables, a quarter with lean protein, and the remaining quarter with a whole grain or starchy vegetable.
Healthy Snacking
Healthy snacks can be part of your meal plan and help with hunger management between meals. Choose snacks that offer a combination of protein, healthy fats, and fiber, with or without carbohydrates.
General Dietary Guidelines
- Eat three small- to moderate-sized meals and one or more snacks each day.
- Do not skip meals and snacks.
- Keep the amount and types of food (carbohydrates, fats, and proteins) about the same from day to day to help stabilize blood sugar levels.
- Prioritize whole fruits and vegetables.
- Choose moderate amounts of lean proteins and healthy fats.
- Incorporate moderate amounts of whole grains and starchy vegetables.
- Limit foods with a lot of sugar, such as soft drinks, fruit juices, and pastries.
Specific Food Choices
- Grains, Beans, and Starchy Vegetables: Choose whole-grain options loaded with vitamins, minerals, fiber, and healthy carbohydrates.
- Vegetables: Enjoy a variety of vegetables, as most do not significantly raise blood glucose levels and provide essential nutrients.
- Fruits: Opt for whole fruits rather than juices, and choose citrus fruits for their nutritional benefits.
- Milk and Dairy: Select low-fat or nonfat dairy products, avoiding those with added sugar or artificial sweeteners.
- Protein: Choose lean protein sources such as fish, poultry, and lean cuts of meat, prepared through baking, roasting, broiling, or grilling.
- Sweets: Limit the consumption of sweets due to their high fat and sugar content, and be mindful of sugar-free options that may still contain carbohydrates.
- Fats: Limit overall fat intake, focusing on healthy oils such as canola, olive, peanut, and safflower oil, and include nuts, avocados, and olives in moderation.
The Role of Remote Patient Monitoring (RPM)
Remote patient monitoring (RPM) is a valuable tool for pregnant women to track their blood sugar levels from home. When combined with a comprehensive normal blood sugar levels chart, RPM provides a powerful tool for prenatal care, especially for gestational diabetes. RPM allows for continuous monitoring of blood sugar levels without the need for frequent in-person visits to a healthcare provider.
A comprehensive normal blood sugar levels chart for pregnancy is an essential component of RPM. This chart provides guidelines for what constitutes normal blood sugar levels at various stages of pregnancy and after meals, helping women identify patterns in their blood sugar levels and work with their healthcare provider to adjust their treatment plan as needed.
Normal Blood Sugar Levels During Pregnancy
Maintaining optimal blood sugar levels during pregnancy is essential for a healthy mother and baby. The following are general guidelines to aim for:
- Fasting: 70-95 mg/dL
- 1 Hour Post-Meal: Less than 140 mg/dL
- 2 Hours Post-Meal: Less than 120 mg/dL
Individual target levels may vary based on personal medical history and the advice of a healthcare provider.
Additional Lifestyle Changes
In addition to dietary changes, regular physical activity is important for managing GDM. Aim for at least 30 minutes of moderate-intensity physical activity most days of the week, after consulting with your healthcare provider.