Gestational Diabetes Glucose Test

A gestational diabetes glucose test will be recommended around 26 weeks of pregnancy – usually between 24 and 28 weeks. During every appointment, your urine will be tested for signs of glucose – among other things. If at any time you have glucose in your urine, the 1 hour glucose tolerance test may be performed sooner than 26 weeks.

 Gestational Diabetes Glucose Test
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What is Gestational Diabetes?

Gestational diabetes is diabetes – or high blood sugar – that is diagnosed during pregnancy. Gestational diabetes is usually harmless to you – the mother – but if left undiagnosed, it can be deadly to your baby.

Gestational diabetes is the most common complication of pregnancy and it affects 2 to 7% of all pregnancies.

In you, the mother, there are usually few – if any – symptoms that something is amiss. In your baby however, gestational diabetes could lead to:

  • Macrosomia (larger size at birth) resulting in an increased risk of birth injuries and delivery by c-section
  • Increased chance of diabetes and obesity later on in life
  • Increased risk of jaundice
  • Hypoglycemia – Low blood sugar in your baby after birth
  • Neonatal death – this is a rare complication but possible

You can therefore see why your birth practitioner will test your urine for signs of glucose at every visit.


What are the risk factors for gestational diabetes?

  • Family history of diabetes – parents, siblings, grand-parents
  • History of previous – and unexplained – stillbirth
  • If you have given birth to a baby previously weighing over 9 lbs
  • Non-pregnant weight of over 180 pounds
  • 2 consecutive positive clean catch specimens NOT explained by dietary intake
  • Signs and symptoms of diabetes:
  • Excessive urine output
  • Excessive thirst
  • Excessive eating
  • Weight loss
  • Poor healing
  • Preeclampsia or chronic high blood pressure
  • Excessive amniotic fluid – polyhydramnios
  • Age – 25 or older
  • Gestational diabetes in a previous pregnancy
  • Ethnicity

Gestational Diabetes Glucose Test:

The 1 hour Glucose Tolerance Test

While wanting to rule out this condition is a wonderful idea, many believe that the 1 hour glucose stress test – which is a glucose load test – may not be the best way to do so.


How is the 1 hour glucose tolerance test performed?

Upon arrival for your test, you will be given 50 grams of pure glucose. This sugar solution tastes like an overly sweet flat orange soda. You may also be asked to fast before the test.

After one hour, your blood will be drawn.

Note: fasting glucose levels are unreliable for GD.

A blood glucose level greater than 140 milligrams suggests gestational diabetes. Yes, suggests only, for this reason if your 1 hour glucose tolerance test was positive, a 3 hour glucose tolerance test will need to confirm this diagnosis as true gestational diabetes diagnosis.


What are the draw backs to the 1 hour glucose tolerance test?

For one, the 1 hour glucose tolerance test is NOT a diagnostic test for gestational diabetes. If you test positive, you will have to submit to a 3 hour gestational tolerance test which not only require at least 8 hours of fasting but is also notoriously inaccurate!

This test is also controversial because this oral glucose tolerance test – OGTT – takes no previous dietary history into consideration. It has also been determined by various studies – one in a 1991 study by Dr. Keen- that the weight of your baby at birth has more to do with other risk factors such as your race, age, the number of previous pregnancies and your weight at conception.

Second, giving you a concentrated refined sugar load – especially after fasting – can create a physiological reaction to a sugar overload which will mimic diabetes. This is called starvation diabetes. In this case, starvation diabetes is a physiological shock reaction to a gestational diabetes glucose test (either a 1 hour or a 3 hour) not true diabetes. Also because it can take your body up to 6 hours to return to normal, the 1 and 3 hour glucose tolerance tests cannot be used as good tools to detect this condition.

Moreover, a huge substantial epidemiological research project which produced a research paper called “Effective Care During Pregnancy and Birth,” concluded that the 1 hour glucose tolerance test as well as the 3 hour glucose tolerance test should be abandoned because the fasting and the glucose load made them unreliable and dangerous for some women and their babies. This same paper only recommended random glucose screening or a 2 hour postprandial glucose test.


So how common are false positives with this gestational diabetes test?

1/3 of women with a positive 1 hour glucose tolerance test will not have gestational diabetes. Some say false positives are much higher than that since the 3 hour glucose tolerance test is also unreliable.


Gestational Diabetes Glucose Test by Florence

When I was pregnant with my first, I ‘failed’ my 1 hour glucose tolerance test. I also spilled sugar in my urine every time I had orange juice for breakfast.

At the time, I spoke with Doctor Brewer who said that this test was lousy (his words.) First, he considered it dangerous on two levels: 1) The 12 hour fasting and 2) The carb load with simple sugars.

Doctor Brewer explained to me that since your kidneys have to work quite hard to excrete the waste materials for you and for your baby, they sometimes get “lazy” and let larger molecules go through.

In my case, orange juice could not be handled by my kidneys. I gave it up and was fine. Luckily, my 3 hour tolerance test was fine but it was quite awful and made me very sick. I almost passed out and spent the rest of the day in bed. I am surprised I was able to drive home at all.

I said never again. The only test for gestational diabetes I have ever submitted to since was a 2 hour postprandial test.


Note: Some women do get sick during the 1 hour glucose tolerance test even though this is much more common during the 3 hour glucose tolerance test.

Gestational Diabetes Glucose Test:

The 3 hour Glucose Tolerance Test

You will need to prepare carefully for this test.

Three days before this gestational diabetes glucose test, you will be asked to do a carb load by eating at least 150 grams of carbohydrates a day. If you have a healthy diet that is equivalent to about 1 slice of bread per meal.

For 8 to 14 hours before the test, depending on your birth attendant, you will be asked to fast. You will be allowed water and nothing else.

Since you are fasting, the test is usually scheduled early morning. Your blood will be first drawn upon arrival. Then you will be asked to drink a concentrated glucose solution. Your blood will then be drawn again at 1 hour, 2 hours, and finally 3 hours (hence the name: 3 hour glucose tolerance test.)

This test, like the 1 hour glucose tolerance is unreliable and can mimic diabetes – starvation diabetes.


3 hour Gestational Tolerance Test Results: Abnormal Results
Fasting 90 mg/100 ml of whole blood – or higher
One hour 165 mg/100 ml of whole blood – or higher
Two hour 145 mg/100 ml of whole blood – or higher
Three hour 125 mg/100 ml of whole blood – or higher


Notes: If you results are above these numbers, you will be said to have gestational diabetes. If plasma is used rather than whole blood, the values need to be increased by 15%.



Gestational Diabetes Glucose Test:

The 2 hour Postprandial Glucose Test

You may not be familiar with this gestational diabetes glucose test. So what is it? A 2-hour postprandial glucose test – 2-hour PPG – is a gestational diabetes test which is performed 2 hour after a normal meal.


How do I prepare for a 2 hour postprandial glucose test?

Anne Frye in her book “Holistic Midwifery” has these recommendations:

  • 3 days prior to the test, do a carb load. Eat complex carbohydrates no white sugar or white flour. One extra slice of bread per meal should about do it.
  • Fast from dinner to breakfast – about 8 hours.

Once you arrive for your appointment, a finger prick will be done. The value should be less than a 120.

You will then be asked to have a large breakfast.

Walking after eating is a good idea.

At 2 hours after your breakfast, another finger prick will be performed. This value should be less than 140.

Note: Some midwives are okay with just the finger prick after breakfast.


Gestational Diabetes Glucose Test:

What if I am Diagnosed with Gestational Diabetes?

Your birth attendant should give you dietary guidelines in order to help you manage your gestational diabetes naturally. Sound nutrition and exercise should be key in managing this condition.

If you were planning on a homebirth or a birth center birth, gestational diabetes should NOT disqualify you as long as it is managed and under control.

If you attendant is not willing to work with you, find another one!



Sources and further reading for Gestational Diabetes Glucose Test:


Comment about Gestational Diabetes Glucose Test

  • GTT sick everywhere by Emma (essex)

Just had my GTT and after the 2 hours and final amount of blood was taken I felt a bit queasy. I then went to the toilet where I was sick a lot and felt light-headed and hot and sweaty and looked green. I was sat down given water then toast and felt better – but I feel a bit queasy now a few hours later and am desperate to get my result.

Feb 28, 2012 ~ Gestational diabetes by  Natural Motherhood

I am so sorry you were so sick…that was my experience as well and my test was negative for GD. Pumping sugar into our blood stream is just a very dumb way to test.


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