The Gestational Diabetes Test Explained

Has your doctor mentioned that it’s almost time to be screened for gestational diabetes? 

If this is your first pregnancy you may be totally caught off guard. In today’s blog post we’re going to cover all things gestational diabetes.I’m going to walk through what gestational diabetes is, what the screening test involves, how to prepare, interpreting your results, and next steps.

Ready to get reading? Let’s dive in!

Gestational Diabetes 

Gestational Diabetes is a type of diabetes that usually only pops up during pregnancy. Most individuals diagnosed with gestational diabetes did not have diabetes prior to pregnancy and will not have diabetes after the baby is born. It is recommended that all pregnant individuals should be screened for gestational diabetes between 24 and 28 weeks. 

With gestational diabetes, there is not enough insulin produced (a hormone that helps control blood sugar levels) to support the growing baby and changing hormone levels. Unfortunately, when blood sugar levels are not well controlled, it can have negative effects for both the mom and the baby such as:

• The development of preeclampsia (high blood pressure)

• Poor blood sugar control in the baby 

• A larger than average sized baby 

• Increased difficulty during labor and delivery

Risk Factors

There are a number of risk factors that can contribute to your risk of developing gestational diabetes such as:

• Age (those over 35)

• Race (African, Arab, Asian, Hispanic, Indigenous, or South Asian)

• Use of corticosteroid medications

• Prediabetes diagnosis prior to pregnancy

• Body Mass Index (BMI) above 30

• History of birthing a large baby (> 10lbs)

• Family history of type 2 diabetes

• Diagnosis of PCOS or acanthosis nigricans

• Lifestyle factors (e.g. diet and activity levels) 

You failed the screening, now what?

I know that it’s easier said than done, but if you discover that you failed your screening test, try not to panic! This test is extremely sensitive and designed to pick up everyone that COULD have gestational diabetes. Even if you fail, it does not automatically mean you have gestational diabetes. 

If you did not pass the screening test, it will be recommended that you have a second diagnostic test completed. I can cover this second test in more detail in another blog post if you are interested. It is a longer test and you must fast prior.  

For most people, gestational diabetes can be well managed by monitoring blood sugars, eating a healthy diet, and staying active. Working with a dietitian during this stage can be extremely helpful! 

In some cases, diet and lifestyle changes may not be enough to manage blood sugars. If this is the case, you may be prescribed certain medications or insulin. At this point you should be referred to a diabetes education center for one-on-one support with a diabetes educator. 

What is the test?

The gestational diabetes screening test is a measurement of your blood sugar levels after drinking 50g of glucose. You won't be required to fast prior to this screening. You simply show up to the lab and hand them your requisition. 

They will hand you a drink (sometimes flavored, sometimes not) that contains 50g of glucose and you will have 5 minutes to finish it. Once finished, a timer will be set for 1 hour. During this time you will be asked to sit still and wait. Once the hour is up, they will draw your blood and you can go home. 

Preparing for the test 

There is a lot of misinformation out there regarding the gestational diabetes screening test. I’ve seen people encouraging others to do anything from eating only “healthy” foods a couple of weeks prior to the test, to eliminating carbs altogether, and even recommending others to complete the test fasted. 

Although some of these tips may sound tempting ecause let’s be honest, none of us want to hear that we have gestational diabetes,it’s best to follow your practitioner's instructions. It’s not a good idea to try and sway the results in any particular way because a diagnosis of gestational diabetes going undetected could just lead to complications for both mom and baby further down the road.

This screening test does not require fasting, your practitioner just wants to get an idea of how your blood sugar levels are managed under normal circumstances. Should the results of this test look off, you’ll be asked to complete a fasted test. 

So, other than getting a good night's rest, staying hydrated, and eating your typical meals and snacks you really don’t need to (and shouldn’t) prepare for this screening!

Interpreting Results 

There is only one result your practitioner will be looking at to determine if you passed the gestational diabetes screening test, and that is your blood glucose levels one hour after ingesting the 50g glucose drink. 

If your blood glucose levels were below 7.8mmol/L 1 hr after, you passed the screening test. A blood glucose level between 7.8 and 11.0 mmol/L means that gestational diabetes COULD be present and further testing is needed. A result equal to or greater than 11.1mmol/L means it is very likely you have gestational diabetes. 

Next Steps 

Your practitioner will likely review the results of your screening test with you and go over next steps if necessary. If you passed the test, you may not hear back until your next prenatal visit with them (I usually take this as a good sign!). 

If you are in the gray area, or your results show that you could likely have gestational diabetes, you will most likely be required to complete further testing. As I mentioned earlier, this next test is typically fasted and is diagnostic.  This means that it is designed so that only those with gestational diabetes fail. The test is much longer (typically 3 hours in Canada), and they will draw your blood more frequently.

Wrapping Up

As always, if you enjoyed this blog post and found it helpful, I would love to hear from you in the comments! If there is interest, I would be happy to do a blog post explaining the 3 hour test in more detail in the future. 

If you have completed the screening test, what was your experience like?