Not So Sweet – Glucose Tolerance Test and Gestational Diabetes Information

Between 24 and 28 weeks gestation, most OBs and midwives send pregnant woman for the dreaded glucose tolerance test (GTT). This one-hour test is designed to determine who is at risk for gestational diabetes. In this article, I will detail everything you need to know about the test, what gestational diabetes is, and how to read the test results when you attain them. Let’s begin:

What Is Gestational Diabetes?

Gestational diabetes is a condition that affects three to five percent of pregnant women. The placenta, the organ responsible for nourishing the growing baby, produces pregnancy hormones that can interfere with the body’s ability to make or use insulin. In some women, gestational diabetes occurs when the pancreas over produces insulin to accommodate the insulin resistance caused by the placenta. Causing the need to produce up to three times the normal amount of insulin, gestational diabetes puts the woman at risk for a large baby at birth, preeclampsia, premature delivery, and type II diabetes later in life. Her baby will be at risk for hypoglycemia after birth and type II diabetes as it gets older. With proper diet and monitoring, the risks of gestational diabetes can be minimized.

What to Expect During the Glucose Tolerance Test

Women taking the one-hour GTT will receive a sugary drink with 50 grams of glucose. Three popular flavors of the drink include orange, fruit punch and lemon-lime. Many women describe the taste as flat soda or a melted popsicle.

Pregnant women are given five minutes to finish the drink and will not be permitted to eat or drink anything else during the test. A nurse or lab technician will draw blood exactly one hour later.

Although many women feel little side effects from the drink, some moms-to-be may get headaches or extreme fatigue from the intense sugar rush and subsequent crash. Women may also notice a sharp increase in fetal movement, which is perfectly normal.

Furthermore, pregnant women are not required to fast prior to the one-hour GTT, but are required to stay away from high-carb and sugary foods. If you do eat before the test, you should be safe and finish the meal at least one hour before your scheduled appointment. Meals high in protein, such as chicken or eggs, are best because they will not interfere with glucose readings. Lastly, you are encouraged to drink water prior to the test.

How to Read the Glucose Tolerance Test Results

The blood test revels a woman’s glucose level at about one hour after consumption of the drink. The number tells the doctor whether or not the patient is at risk for gestational diabetes. The American Diabetes Association approves doctors using either 130 mg/dL or 140 mg/dL as the passing limit. If a woman’s levels fall below the cut off line, she does not have gestational diabetes. However, if she fails the test, she still may not actually have gestational diabetes.

Having a higher blood glucose level than the passing cutoff suggests that the woman is at a higher risk for gestational diabetes. If this occurs, the next step is that the doctor will schedule an appointment for the three-hour glucose tolerance test, which is used as the main diagnostic tool rather than an indication of risk (which is the purpose of the first, initial test).

Approximately 20% of pregnant women fail the one-hour preliminary glucose tolerance test, however only four percent actually progress and are diagnosed with gestational diabetes after the three-hour test.

gestational diabetes pregnancy

What to Expect During the Three-Hour Glucose Tolerance Test

Depending on the doctor, women will be required to fast prior to the three-hour GTT for eight to 12 hours, with the ability to drink water until the test begins. Although pregnant women are encouraged to eat normally the day before the test, choosing foods high in protein and low in carbohydrates and sugars will help ensure no false-positive results.

Before being given the drink, patients going through the three-hour GTT will have a fasting blood draw. This allows the doctors to see what the body’s blood sugar level is without the influence of food and drink. Pregnant women will then be given five minutes to drink the glucose juice. The sugary drink for the three-hour test typically is available in the same flavors as the one-hour test, but the drink contains 100 grams of glucose.

Women who had no side effects from the 50-gram juice may suffer from a headache or a tired feeling during this test. Feeling more baby movement is a completely normal side effect of the glucose drink. Patients will have blood drawn at exactly one hour, two hours and three hours after finishing the drink.

Reading the Results of the Three-Hour Test

Typically, if zero or one of the four blood draws is above the pre-set limits, the patient is not diagnosed with gestational diabetes. The cutoffs are as follows:

  • Fasting – 95 mg/dL
  • One-Hour – 180 mg/dL
  • Two-Hour – 155 mg/dL
  • Three-Hour – 140 mg/dL

Women with two or more abnormal levels, which accounts to about three to five percent of pregnant women, are positively diagnosed with gestational diabetes. In many cases, gestational diabetes can be controlled with close monitoring of carbohydrate intake and exercise. These moms-to-be will be referred to or should ask to see a diabetic nutritionist so that a gestational diabetes meal plan can be administered. On more rare and severe instances, women may have to use insulin to help control the gestational diabetes.

The glucose tolerance test is an important rite of passage into the second half of the pregnancy cycle. Pregnant women should talk to their doctors about risk factors, symptoms and testing of gestational diabetes to ensure the best possible health for the mother and her baby. Just remember, having the knowledge and acting proactively can make all the difference in preventing serious side effects during pregnancy, at birth, and in the post natal phase. Share this article and spread the knowledge to all pregnant women out there. It’s important!