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Glucose Screening And Glucose Tolerance Test During Pregnancy

5 min read

All pregnant women are screened for potential gestational diabetes during their pregnancy. Screening is done by evaluating the woman’s medical history and examining certain risk factors including obesity and family history of diabetes. Certain tests like Glucose Screening Test and Glucose tolerance test are also recommended. Read on to know more about these tests.
glucose screening test

What Is Glucose-Screening Test?

The glucose-screening test is a routine test recommended for all pregnant women. The glucose – screening test is normally done during the second trimester of pregnancy between 24th and 28th week. The objective of this test is to screen for gestational diabetes. Gestational diabetes is a form of diabetes that appears only during the pregnancy time and will disappear after delivery. It can cause several serious issues as the pregnancy progresses.
If your routine prenatal urine test shows readings that are above normal reading of glucose or if you have an increased chance of gestational diabetes, the test will be performed earlier.

Who Needs To Take The Glucose Screening Test And Why?

Around fifty percent of the women who develop gestational diabetes are found to possess no known risk factors. Therefore, this test is included among the other routine tests conducted in the course of pregnancy. This test will be conducted little earlier than the usual time, if you:

  • Have had gestational diabetes in your earlier pregnancies
  • Are obese
  • Are over 30 years old
  • Have a family history of diabetes
  • The urine tests during the early months show an increased level of sugar
How Is The Glucose-Screening Test Performed?

As in the case of all screening tests, the glucose-screening test is not a diagnostic test. The positive result only implies that you need to undertake additional tests to confirm gestational diabetes.
Blood sugar in pregnancy
For glucose-screening test:

  1. There are no restrictions on eating or drinking prior to this test. You can go as usual for your prenatal visit and the test will be performed
  2. You will be asked to drink a liquid that contains glucose (mostly flavored one, as you may develop an aversion to non-flavored fluids during pregnancy). You have to drink down this solution in five minutes
  3. You have to wait for an hour after drinking the liquid. Post that your blood sample is taken and sent to the laboratory for testing sugar levels

If the reading shows more than the normal level of sugar, glucose tolerant test is performed to confirm gestational diabetes.

How Are The Glucose Screening Test Results Interpreted?

A woman is considered to have normal blood sugar levels if her reading is below 140mg/dl. However, some doctors consider a reading below 130mg/dl as normal. Though several “false” positive results can appear when normal reading is considered below 130mg/dl but in this way the doctors are able to recognize more patients who have a chance to develop gestational diabetes.
If the reading is above 200mg/dl, then the patient is considered to have gestational diabetes. In such case there is no need for conducting any further test.
However, if the reading is in between 140mg/dl to 200mg/dl, glucose tolerance test is ordered by the doctor to confirm gestational diabetes.

What Is Glucose Tolerance Test?

If the glucose-screening test results are above normal, the next step is to perform a glucose tolerance test. This test result will confirm gestational diabetes.

How Is The Glucose Tolerance Test Performed?

Unlike glucose screening test, you have to prepare beforehand for glucose tolerance test.

  • As the first step, you should mention to your doctor if you are taking any particular medicine other than the one prescribed by your doctor. This will help the doctor to analyze the chances of that medicine influencing the result of the test. You may be required to stop the consumption of that medicine before a few days of the test as instructed by the doctor
  • You can have a normal dinner the night before the test. After that, you are not supposed to eat or drink anything other than water for 8-14 hrs. before the test
  • The test is scheduled first thing in the morning
  • As soon as you reach the lab, a blood sample is taken to find out the fasting blood sugar
  • Highly concentrated glucose solution will then be given as the next step of the procedure. You have to drink it in two to five minutes
  • Once every hour, for the next three hours, your blood sample is collected. This way the readings of blood sugar levels after one hour, two hours and three hours respectively are evaluated

Glucose tolerance test

How Are The Glucose Tolerance Test Results Interpreted?

Abnormal values for the glucose tolerance test are:

  • Fasting sugar: 95 mg/dl or higher
  • After one hour: 180 mg/dl or higher
  • After two hours:155 mg/dl or higher
  • After three hours: 140 mg/dl or higher

If any of the above abnormal value shows up in your test results and all other readings are normal, the doctor will suggest some changes in your diet and ask you to start some mild exercises like walking or increase the duration your exercise if you are already doing it. More than one abnormal value in your test result confirms gestational diabetes.

Side Effects of Glucose Tolerance Test

Many women don’t face any kind of side effect after undertaking the glucose tolerance test. Drinking the glucose solution is like drinking a very sweet beverage. In some cases, women may feel nauseated and may even throw up after they drink the glucose solution. If they vomit soon after they have had the glucose drink down, they will have to come back some other day and repeat the test.
Severe side effects from this test are not known.
However, here are a few important things that you have to keep in mind when you go for the glucose tolerant test:

  • Bring along a book to read in order to pass time as you have to spend three hours in the lab
  • Take a small box of food with you as you may be famished and want to eat as soon as you finish the test
  • Never try to drive by yourself after the test as there are chances you may feel dizzy because of the test and definitely your energy levels will be very low after completing this test
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