Medical Nutrition Therapy for Gestational Diabetes Mellitus
Gestational diabetes mellitus (GDM) affects 1 in 6 women in Australia, being associated with a significant number of adverse maternal and neonatal outcomes, such as preeclampsia, clinical neonatal hypoglycaemia and larger birth weight. Medical nutrition therapy (MNT) is important for managing gestational diabetes mellitus (GDM). All pregnant women with GDM should get Medical Nutrition Therapy (MNT) as soon as diagnosis is made.
Goals and Principles of MNT
Medical nutrition therapy has a role in managing gestational diabetes, with the main goals being to meet the nutritional requirements of pregnancy, achieve glycaemic targets, and reduce the risk of adverse maternal and neonatal outcomes. MNT for GDM primarily involves a carbohydrate controlled balanced meal plan which promotes optimal nutrition for maternal and fetal health, adequate energy for appropriate gestational weight gain, and the achievement and maintenance of normoglycemia.
Individualised Nutrition Assessment
Nutrition assessment in GDM should be individualised to allow an accurate appraisal of the woman’s nutritional status. Individualized nutrition assessment and calorie needs based on pre-pregnancy weight and weight gain targets are important. This assessment includes defining her Body Mass Index (BMI) or percentage of desirable pre-pregnancy body weight and optimal pattern of weight gain during pregnancy.
Specifically, the BMI is calculated as: BMI (kg/m2) = weight in kg / height in meter square. Routine weight monitoring is also recommended and should be encouraged throughout pregnancy to reduce the risk of adverse health outcomes for both the mother and the developing baby.
Caloric Requirements During Pregnancy
Energy requirement during pregnancy includes the normal requirement of adult and an additional requirement for fetal growth plus the increase in the body weight of pregnant woman. Energy requirement does not increase in the first trimester unless a woman is underweight, but it increases during second and third trimester. Energy intake should be adequate enough to provide appropriate weight gain during pregnancy.
As per Indian ICMR guidelines, for an average weight gain of 10-12 Kg, an addition of 350 kcal/day above the adult requirement is recommended during second and third trimester. Severe caloric restriction is not recommended as it may result in ketonemia and ketonuria and impair physical and mental development in offspring. To determine specific needs, equations proposed by the ICMR expert group can be used to calculate adult energy requirement:
- Energy requirement (kcal/d) = BMR × PAL
- *BMR = Basal metabolic rate
- *PAL = Physical activity level
| Age Group | BMR Calculation (kcal/d) |
|---|---|
| Adult females (18-30 yrs) | 14 × B.W (Kg) + 471 |
| Adult females (30-60 yrs) | 8.3 × B.W (Kg) + 788 |
Furthermore, the number of calories necessary to maintain 1 kg of body weight varies: 30 kcal for average weight women (80-120% of ideal body weight) and 35-40 kcal for underweight women.
Macronutrient Composition and Dietary Recommendations
The recommended macronutrient composition generally ranges from 50-60% carbohydrates, 10-20% protein, and 25-30% fat. However, specific caloric distribution can be structured as follows:
| Carbohydrate | Fat | Protein |
|---|---|---|
| 55 % | 20 % | 25 % |
Complex carbohydrates should be emphasized over simple carbohydrates, and protein intake is increased in pregnancy. The Academy of Nutrition and Dietetics recommends low glycaemic index carbohydrates or the DASH Diet, with a total carbohydrate consumption of 175g or more per day (or 36-65% of estimated energy requirements). Regarding specific diets, caution should be taken before recommending a ketone diet, as ketones may impair foetal and postnatal neural development.
Management of Glycemic Control
Failure to maintain glycemic control through lifestyle changes alone may require insulin therapy. Additionally, hypoglycemia should be treated immediately with glucose or sugary foods. Working alongside a multidisciplinary team, optimising nutritional adequacy and dietary variety, while also recommending weight monitoring during pregnancy, can help to ensure that the risks associated with gestational diabetes are minimised.