How to perform the Glucose Challenge Test during pregnancy? 

The glucose challenge test is done early during your pregnancy to measure the response of your body to glucose (sugar). It is a screening test for gestational diabetes, which is a condition that develops in some women during pregnancy. The test is quite simple where you’re required to gulp down a concentrated sugar solution so they can measure the glucose levels in your blood an hour later. If the levels are higher than expected, there will be more tests for a final diagnosis. 

What the studies show: In India, more than 5 million women are affected by Gestational Diabetes annually.

Gestational diabetes is a type of diabetes that is diagnosed during pregnancy. It happens when the body is not able to produce all the insulin it requires during pregnancy. The hormonal changes along with lowered insulin levels can lead to the development of insulin resistance. The end result is that the blood has a high glucose build-up which can lead to complications such as: 

• Requiring a C-section delivery
• Diabetes risk in the future
• Excessive birth weight in the baby
• Preterm birth
• Low blood sugar in the baby after birth
• Obesity and type – 2 diabetes later in life
• High blood pressure and preeclampsia

What are your chances of getting gestational diabetes? 

There are several risk factors for gestational diabetes, such as: 

• A family history of diabetes
• Gestational diabetes in a previous pregnancy
• Having diabetes risk factor such as obesity
• High blood pressure
• Physically inactive, sedentary lifestyle 
• Older age

Why is the glucose challenge test done? 

The glucose challenge test is done between 24 and 28 weeks of pregnancy to screen for gestational diabetes. The test can also be done as early as the first prenatal visit if you have a high risk of gestational diabetes because of factors such as a family history of diabetes, a personal history of gestational diabetes, pre-existing type-2 diabetes if it was unknown earlier or obesity. Most women who have the condition go on to deliver healthy babies when it is managed carefully. Otherwise, gestational diabetes increases the risk of several pregnancy complications such as excess fetal growth or preeclampsia, which can increase the risk of injuries during birth or the need for a C-section delivery.

There are two ways in which the glucose challenge test is done: 

1. Two-Step Testing

When the glucose challenge test is done as a two-step procedure, there is no need for you to prepare for it. When you arrive at your health care provider’s lab or clinic for the test, you will be given a glass (about 150 millilitres) of concentrated sugar syrup, which contains 50 grams of sugar. You will have to drink it up and wait for an hour at the lab to be tested. 

An hour later, a technician will draw a sample of blood from a vein in your arm. The blood sample will be used to measure the glucose level in your blood. If the glucose level is too high, you will be asked to return for a glucose tolerance test that lasts for 3 hours. 

For the 3-hour glucose tolerance test, you should not eat or drink anything 8-14 hours prior to the test except sips of water. You also won’t be allowed to eat during the test. This time you will be asked to drink a solution that contains 75g of glucose. Your blood is drawn once before you are given the solution and three times again after you drink the solution with an interval of 60 minutes. This is done to measure the glucose level at every hour. 

2. One-Step Testing 

For this test, you must not eat or drink anything except sips of water for 8 to 14 hours before the test. Also, you won’t be allowed to eat during the 2 hour period that the test lasts. Your blood is drawn before you are given a glucose solution containing 75g of glucose to drink. Your blood is drawn two more times again with a 2-hour interval to check for glucose levels.

The glucose challenge test results will indicate the blood glucose levels that are measured in milligrams per deciliter (mg/dL) or millimoles per litre (mmol/L). These values are applicable to the two-step testing:

• If the blood glucose level is below 140 mg/dL or 7.8 mmol/L, it is considered normal. 
• If the blood glucose level is at 140 mg/dL or 7.8 mmol/L or higher, it could indicate gestational diabetes. 
• If the blood glucose level is higher than 190 mg/dL or 10.6 mmol/L after an hour, then it’s a positive diagnosis for gestational diabetes. 

It’s essential to remember that some labs have a lower threshold for normal at 130 mg/dL or 7.2  mmol/L for the glucose challenge test. 

Conclusion

The glucose challenge test is done during pregnancy to screen for gestational diabetes. Women who have risk factors associated with diabetes are more likely to develop the condition. However, it is possible to prevent gestational diabetes or reduce the risk through lifestyle changes such as staying active, eating healthy foods, starting pregnancy at a healthy weight and not gaining any more weight than recommended. 

References: 

https://www.mayoclinic.org/tests-procedures/glucose-challenge-test/about/pac-20394277 

https://www.medicalnewstoday.com/articles/312625#risks-and-side-effects 

https://medlineplus.gov/ency/article/007562.htm 

https://www.mayoclinic.org/diseases-conditions/gestational-diabetes/symptoms-causes/syc-20355339#:~:text=Gestational%20diabetes%20is%20diabetes%20diagnosed,pregnancy%20and%20your%20baby’s%20health. 

https://www.1mg.com/labs/test/glucose-challenge-test-pregnancy-32624