Monday, June 30, 2014

Gestational diabetes mellitus (GDM): Glucose Challenge Test or Glucose Tolerance Test (GTT)


What is gestational diabetes?
The hormone insulin moves glucose or sugar from your blood and into your body’s cells, where it is used for energy. When you have diabetes, this process is blocked and your cells become “insulin resistant”.  This causes you to have too much glucose in your blood. In pregnancy, the hormones from the placenta, which help your baby to grow, can cause your cells to become insulin resistant. Usually in pregnancy the body produces more insulin to counter this but in some mothers this doesn’t happen and they develop gestational diabetes.
There are many health issues associated with gestational diabetes, including the fact that both the mother and baby will have an increased risk of developing type 2 diabetes later in life. During the pregnancy, gestational diabetes can lead to excessive sugars and fats crossing the placenta, which can have an effect on the baby’s growth, usually making them bigger. Giving birth to larger babies can also lead to problems with the birth. Sometimes, even though it might not seem to make sense, some babies (particularly larger babies) are born with blood sugar levels that are too low – this is called hypoglycemia. 
Who are more likely to get gestational diabetes (GDM)?
  • older mothers 
  • women who have a family history of type 2 diabetes
  • women who are overweight
  • women who are from certain ethnic backgrounds; including, South Asian, Vietnamese, Chinese, Middle Eastern and Polynesian/Melanesian.
  • Other women at risk include those who have had gestational diabetes, polycystic ovarian syndrome, large babies or birth complications in the past

Testing for gestational diabetes

During pregnancy, women are generally offered a test to screen for glucose (called a Glucose Challenge Test). The screening test can identify women who may have elevated blood sugars. If you have elevated blood sugar levels you will be offered a Glucose Tolerance Test (GTT). The GTT assesses how your body responds to a 'glucose load' or how efficiently the glucose is moved from your blood to your body’s cells. You are required to fast for 8 to 12 hours and then you have a blood test. After the blood test you have a drink that contains glucose. One or two hours after you have the drink another blood test is done. Gestational diabetes will be diagnosed if your blood sugar levels are above what they should be.

This test is used to screen for Gestational Diabetes and is usually performed at about 26 -28 weeks.
  • The test requires you to have a very sweet glucose drink and then return for a blood test exactly one hour later.
  • You are not required to fast but you can have a light breakfast or meal prior to the test. Do not over indulge in sweet foods and drinks prior to the test.
  • If you are having the test at Suite 6 go there on your way before your scheduled appointment time here.
  • Come to the rooms for your appointment then return to Suite 6 for your blood to be taken one hour after having your glucose drink.  At the same time you may have blood taken to check for anemia or blood group antibodies.
  • If you haven’t seen your doctor before having your blood taken please let our reception staff knows prior to going back to Suite 6.
  • There is no need to ring for the results as we will contact you if they are abnormal. If you GCT is abnormal this means you need a definitive test i.e.; a Glucose Tolerance Test.  (Some women in the higher risk category may go directly to a GTT).
Difference between GCT and GTT Test

A Glucose Challenge Test (GCT) is a non-fasting screening test which measures the level of blood sugar after the patient has had a drink which contains a specific amount of glucose.  An hour later a blood test is taken to check the blood sugar level.  (The idea of this is to see how efficiently your body processes sugar).  If the level is too high, then you will be required to have a Glucose Tolerance Test (GTT).
A high test result does not necessarily mean that you have Gestational Diabetes.

A Glucose Tolerance Test is a more definitive examination.  This a fasting test performed over two hours (fasting means no food or drinks- apart from water- from 10pm the night before). When you attend for your pathology visit a fasting blood sample is taken. You will then be given a small bottle of gluscose drink. A second blood test will be collected 1 hour later and again 1 hour after that. During this time you are not allowed to drink, eat or smoke. The results of these blood tests are very specific and if elevated will indicate that you have gestational diabetes.  Not every one having a Glucose Tolerance Test will be diagnosed has having gestational diabetes.

What happens if I am diagnosed with gestational diabetes?
You will work with your Obstetrician, a diabetes specialist and a diabetes educator or dietician to come up with a plan to manage your condition.  Your condition should only last as long as your pregnancy.
Your Obstetrician may recommend further ultrasounds later in your pregnancy, and you may have additional monitoring of the baby.  You will learn to measure your blood glucose levels regularly.  Most are managed with diet modifications; however a few women may need to have insulin to bring their sugar levels down during pregnancy.


Managing gestational diabetes 

Gestational diabetes can be managed with healthy eating, physical activity, monitoring your blood glucose levels and sometimes medication. 

Diet 

A good diet can keep your blood sugar levels within target. With diabetes you are encouraged to eat regular meals, eat small amounts but eat often, include some carbohydrate in every meal or snack. 
Foods should be enjoyable and varied, low in saturated fats and high in fiber. Avoid carbohydrates that have little nutritional value like cakes and biscuits or juices and soft drinks. Give preferences to more complex carbohydrates such as multigrain breads and breakfast cereals, pasta and noodles (preferable Doongara or Basmati rice because they have a lower glycemic index). Legumes such as baked beans, red kidney beans and lentils, fruit, Milk and yoghurts. 


Monitoring 

If you have gestational diabetes, you will need to learn how to measure your blood sugar levels. Fifty per cent of women who develop gestational diabetes ultimately develop Type 2 diabetes, so if you have had a gestational diabetes diagnosis, it is very important that you have regular follow-up tests for diabetes after the pregnancy or before becoming pregnant again.

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