Gestational Diabetes: Preparing for your Glucose Tolerance Test

It’s a routine part of pregnancy health care to undergo a Pregnancy Oral Glucose Tolerance Test (POGTT) at around 26-28 weeks. If you are at high risk of Gestational Diabetes (GD), testing may occur earlier. This test is currently performed as a Fasting test, meaning that you are only allowed to consume water in the 10-12 hours prior to the test. The test is often performed first thing in the morning, for this reason.

Blood Glucose (blood sugar) readings will be taken 3 times during this 2 hour test, and Gestational Diabetes will be diagnosed if any of the blood sugar readings are higher than the following (Source):

Fasting >= 5.1 mmol/l

1 hour after consuming the 75g glucose drink > 10 mmol/l

2 hours after consuming the 75g glucose drink > 8 mmol/l

It is interesting to note that when a similar test is completed by a non-pregnant person, the guidelines are different:

For Pre-Diabetes diagnosis, Fasting > 6.1 and 2 hours >7.8; For diagnosis of Diabetes, Fasting >7, 2 hour > 11.1

Anne Frye, in her book Understanding Diagnostic Tests in the Childbearing Year (7th Edition, 2007) presents a detailed plan to ensure that the testing is a true reflection of your ability to process glucose. Eating good quality carbohydrates, along with physical activity helps your body to regulate insulin and blood sugar levels. Her sensible guidelines for the week before the test are as follows:

Drink plenty of water so that you are well hydrated.

During the 3 days before the test, eat 150g per day of GOOD QUALITY CARBOHYDRATES - Wholegrains, beans and starchy vegetables (potatoes, sweet potato, corn, beans, pumpkin, etc) and avoid low quality carbs (sugar, white flour products, processed snacks, processed breakfast cereals etc). This ensures that you are well nourished and your glucose stores (glycogen reserves) are boosted prior to the test.

This example menu will give you approximately 50g of carbohydrate at each meal:

1/2 cup oats for breakfast with milk and blueberries. 2 boiled eggs.

1 cup of Lentil Dahl with 1/2 cup of vegetables for lunch

1 cup of brown rice or 2 cups of starchy vegetables with protein and non-starchy vegetables for dinner

Exercise each day. (Research has shown that 3-15 minutes of exercise after meals is very effective for regulating blood sugar and insulin levels)**

The last meal prior to fasting should be 50g of carbohydrates (10-12 hours before your testing appointment - if your test is at 9am, aim to finish this meal prior to 11pm)

** This link has some great information on the importance of exercise in insulin and blood glucose regulation.