Tests for Gestational Diabetes

Tests for Gestational Diabetes

What you need to know about the oral glucose tests, what the results mean and what you can do if you have gestational diabetes.

Even though it is known that blood sugar levels tend to be higher during pregnancy anyway, and the Cochrane Collaboration states that “the best way of identifying and treating women with abnormal blood glucose tests is not known“, nearly every woman today is screened for gestational diabetes.

What tests are available and what happens if you are diagnosed with gestational diabetes?

When is this test offered?

Most women are routinely screened for gestational diabetes between 24 and 28 weeks of gestation with a one hour oral glucose challenge screening test.

How is the glucose challenge screening test performed?

This oral glucose challenge test is given in a lab or in your doctor or midwife’s office. Mothers are given an oral solution (containing 50g of glucose) to drink, followed by another solution (with plasma glucose) an hour later. A sample of the mother’s blood is then taken. Results are available in one day.

Do I need to fast for the 1 hour glucose challenge screening?

Fasting is not required for the first one hour challenge screening test.

What if I fail the one hour oral glucose challenge for gestational diabetes?

A result of 140mg or higher on the 1 hour challenge screening is considered to be a “positive screen.” The mother will then be tested in a 3 hour glucose tolerance diagnostic test.(OGTT) The three hour OGTT requires an overnight fast. For 3 days prior to the overnight fast, the mother should eat a normal diet (including at least 150g of carbohydrates). It is best to avoid caffeine and smoking since they can raise the level of glucose in the bloodstream.

Check with your provider about other medications you may need to stop as well. Your blood will be drawn first and this is your “fasting” blood sugar level. You will then drink several ounces of glucose solution and have your blood tested again at 1, 2 and 3 hours.

How will I know if I fail the 3 hour OGTT?

The numbers for the 3 hour OGTT test for gestational diabetes are as follows:

Normal – 100mg at 3 hours

Positive (if two of more of the tests results are at the following levels or higher)

  • Fasting – 105mg
  • 1 hour – 190mg
  • 2 hours – 165mg
  • 3 hours – 145mg

Occasionally if a mother has only failed one of the three above tests, the provider might ask you to repeat the 3 hour OGTT.

What if I am diagnosed with “gestational diabetes?”

About 4% of women will be diagnosed with gestational diabetes during their pregnancy. There are several things that you might need to expect if you have been diagnosed with gestational diabetes:

  1. Diet changes – a standard diabetic diet is recommended. Often this involves cutting back or eliminating foods that are high in simple sugars such as cake, cookies, ice cream and juice. See a nutritionist for a diet plan that is specific to your caloric needs based on height, weight, physical activity, etc…
  2. Exercise – Regular exercise 3-4 times a week for 15-30 minutes will help to lower blood glucose levels;
  3. Monitoring blood sugar levels – some providers will recommend mothers should check their own blood sugar at home or have weekly checks at the office.
  4. If the mother is unable to keep her blood sugar levels down with the above strategies, in some situations she may require insulin therapy.

How will gestational diabetes affect my birth and postpartum?

Some providers will recommend that a mother with gestational diabetes be induced or even a cesarean prior to her due date since there is a chance of a baby with “macrosomia” (or a large baby.) There is controversy about whether or not early induction is truly needed or warranted as routine for all women with gestational diabetes.

In fact, the American College of Obstetricians and Gynecologists states, “Suspected fetal macrosomia is not an indication for induction of labor, because induction does not improve maternal or fetal outcomes.“

Be sure to discuss your labor options with your own provider before deciding on an induction. The good news about gestational diabetes is that most women will return to normal blood sugar levels after the baby is born.

Do I have a greater chance of diabetes in the future?

Between 50-60% of women who have had gestational diabetes will develop diabetes later in life, often within 10 years of giving birth. Knowing these statistics, be sure to make lifestyle changes in your diet so that you can reduce your chances of developing Type 2 diabetes.

For more information about prenatal tests, click here.

Have you had gestational diabetes? What helped you keep your blood sugar down? Share it.

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