What is the Glucose Tolerance Test (GTT):

Many women will be recommended to get the GTT by their Health Care Provider. GTT stands for Glucose Tolerance Test. The GTT tests for Gestational Diabetes, which is a type of diabetes that develops during pregnancy. With this type of Diabetes,  normally symptoms subside once your baby is born. If a mum has GD (Gestational Diabetes) she is more susceptible to developing Type Two Diabetes later in life. 

Why are some women offered the GTT?

There are certain risk factors that make you more susceptible to developing GD. If you have any of these risk factors, your antenatal care provider may suggest a GTT to screen for markers. 

Risk factors for GD include:

  • High Body Mass Index (BMI of 30 or higher)

  • Previous large baby (above 9lbs or 4.1kg)

  • Women older than 25 years

  • Poly-cystic Ovarian Syndrome (PCOS)

  • You had GD during a previous pregnancy, or you had an unexplained stillbirth in the past.

  • Family or personal health history. Your risk of developing gestational diabetes increases if you have prediabetes — slightly elevated blood sugar that may be a precursor to type 2 diabetes — or if a close family member, such as a parent or sibling, has type 2 diabetes.

  • Race. For reasons that aren't clear, women who are black, Hispanic, American Indian or Asian are at higher risk to develop gestational diabetes.

So what is involved if you agree to take a GTT? 

Methods can vary slightly from each hospital, but they remain generally the same. The woman is asked eat her normal diet for the days leading up to the test and to fast for 12 hours before the test (this includes no water). She is then asked to attend an appointment with her Health Care Provider early in the morning (usually around 7.30am). 

 You will receive a fasting blood test, as well as 2 more blood tests at hourly intervals with a Glucose Tolerance Test

You will receive a fasting blood test, as well as 2 more blood tests at hourly intervals with a Glucose Tolerance Test

The test then begins with a fasting blood test. After this the woman is given a jug of lucozade or high sugar drink. She is expected to drink this over 10 minutes. The woman is requested not to eat or drink anything else until the test is fully completed. 

Your care provider will then take two more blood tests at hourly intervals to monitor how your body metabolises sugar. You will be expected to stay in the clinic during the testing process so it is a good idea to bring a book or laptop (as I can imagine 3-4 hours sitting there while starving is not fun).

After the test you will be free to head home,  and as you will have been fasting it is probably a good idea to grab something to eat before you hit the road. 

The blood tests are analysed very quickly and you will be contacted the same day if there is any abnormalities showing up. Most hospitals do not contact women if the test is normal so no news is good news in this situation ;) If you are not contacted you continue with you antenatal appointments as normally scheduled. 

 

What are the pros and cons of agreeing to take a GTT?

Pros:

  • If you are found to have GD, it can be carefully controlled to avoid any complications, most women with GD give birth to healthy babies with no complications. However GD, if not carefully managed does carry risk to mother and baby.

Cons:

  • It is not pleasant to fast for 12 hours when you are pregnant.

  • Drinking a full jug of sugary and processed lucozade is not something most pregnant women would choose to do.

  • Blood tests are uncomfortable.

 

Complications that may affect a baby if their mother has uncontrolled GD:

High birth weight – Babies with a birth weight above 9lbs statistically have higher chance of complications during birth. This includes interventions such as ventous or forceps and increased instance of caesarean births. It is important to note that many women can and do give birth to high birth weight babies without complications or interventions (we all know the pressure women are under if they have a ‘big baby’ during scans, GD or not). 

Low Blood Sugar (hypoglycaemia) – Sometimes babies born to mothers with GD develop low blood sugar shortly after birth because their own blood sugar is too high. Lots of regular feeds or in some cases a glucose drip can help to return babies levels to normal. Again it is important to note, many mothers feel pressure to top up with formula if this situation arises, even when their wish is to exclusively breastfeed. These mothers can hand express extra colostrum or breast milk to offer their baby instead. Some mothers with GD choose to express some of their milk antenatally, to have milk for baby after the birth.

Early (Preterm) birth and Respiratory Distress Syndrome – Babies born early may need help with their breathing until their lungs mature. Also, even babies born at term to mothers with GD are at risk of having respiratory distress syndrome. A mothers high blood sugars can put extra strain on babies body as they fight to maintain a normal level. 

In extreme cases untreated gestational diabetes can result in the death of a baby.

 

Complications that may affect a Mother from having uncontrolled GD:

  • High Blood Pressure and Pre-eclampsia – Gestational Diabetes increases your risk of high blood pressure. It can also increase a mothers risk of preeclampsia which can be life threatening to both mother and baby and usually requires birth by caesarean even before term.

  • Future Diabetes – Having Gestational Diabetes increases a mothers risk of getting it in future pregnancies. It also increases risk of developing Type Two Diabetes later in life. Making healthy life style choices such as eating well and exercising can decrease instances. Breastfeeding your baby is also shown to reduce both mother and baby's risk of diabetes later in life.

You do not have to consent to a GTT. It is your choice to make an informed decision – weighing up the pros and cons and deciding what is best for you and your baby. I hope this blog has helped you to understand risk factors and the process of the test itself. 

Doula Jen 

Jen Crawford, Co-Owner & Founder DoulaCare Ireland.

REFERENCES AND FURTHER READING: 

HSE https://www.hse.ie/eng/health/az/D/Diabetes,-gestational/Testing-your-glucose-levels.html

AIMS http://aimsireland.ie/the-glucose-tolerance-test-gtt/

NICE guidelines https://www.nice.org.uk/news/article/new-thresholds-for-diagnosis-of-diabetes-in-pregnancy

WHO guidelines http://apps.who.int/iris/bitstream/10665/85975/1/WHO_NMH_MND_13.2_eng.pdf

Irish Health http://www.irishhealth.com/clin/pregnancy/conditions02.php?con=574#pregnancy