What is the Glucose Challenge Test? Here is Everything You Need to Know About Gestational Diabetes

The one-hour glucose challenge test is a common screening during pregnancy that checks how your body processes glucose. It’s a straightforward, two-step process: first, you drink a sweet beverage, and then, an hour later, a blood sample is taken to measure your blood sugar levels. This test is designed to spot any early signs of gestational diabetes—a form of diabetes that can develop during pregnancy. If your results are above the standard range, you may need additional testing to confirm a diagnosis.

So, what exactly is gestational diabetes? This condition can raise plenty of questions and concerns, so let’s clear the air. I’ll break down what gestational diabetes is, how it’s diagnosed, how it can be managed, and the risk factors that might increase your chances of developing it. 

What is Gestational Diabetes?

Gestational diabetes is a form of diabetes that is first diagnosed in pregnancy. During the early third trimester, a pregnant person’s placenta will start to increase hormone production, and many of these hormones will cause the mother’s body to become “insulin resistant”. 

Insulin is a hormone made by the pancreas that acts like a key to let glucose (sugar) move from the blood into the cells of your body to be used for energy. However, with gestational diabetes, the cell doors are prone to remaining “shut” and glucose accumulates in the blood. The mother’s pancreas will try to produce more insulin to meet the demand and overcome the rising placental hormones, but sometimes she is not successful, and this is when the extra sugar from her blood can cross over to the baby. We will discuss what risks this poses for mom and baby later on.

A gestational diabetes diagnosis doesn’t necessarily mean that there is something wrong with your pancreas or insulin production. While some women have insulin resistance even before they get pregnant and are more likely to have gestational diabetes, many other women simply develop gestational diabetes as a result of some of the major hormonal shifts  and physiological changes that come with pregnancy. During pregnancy, your body makes more hormones and goes through other changes, such as weight gain. These changes cause your body’s cells to use insulin less effectively so that it can’t help manage your blood sugar. 

How Common Is It?

Gestational diabetes is actually quite common. In the United States, about 6% to 9% of pregnant women develop gestational diabetes. This incidence has increased in recent years. Recent studies found that from 2000 to 2010, the percentage of pregnant women with gestational diabetes increased 56%.

Is There Anything You Can Do to Prevent It?

Many women want to know what they can do to help prevent the development of gestational diabetes in pregnancy. Here are are a few steps you can take to reduce your risk:

• Balance your blood sugar - aim to balance your blood sugar prior to pregnancy and in early pregnancy by pairing carbohydrates with healthy fat and protein, and by limiting refined carbohydrates and sugar. Even if you are managing first trimester morning sickness, try to have your comforting carbs in balance. Better blood sugars can mean less nausea.
• Get to a healthy body weight before pregnancy - healthy doesn’t necessarily mean a BMI in the “normal” range. Rather it means a weight that feels comfortable to you, while eating a nutrient-dense diet and being regularly active.
• Consume sufficient protein in early pregnancy - research suggests that inadequate protein consumption during the first trimester may be a risk factor for gestational diabetes. (Nat Med. 2010)
• Consider supplementation - some research suggests that certains supplements can help with the prevention of gestational diabetes. These include myo-inositol and Vitamin D. However, it’s important that you get your levels checked and work with a trusted provider before supplementing.
• Know your risk factors - risk factors such as age, race, ethnicity, or family history are not exactly modifiable, but being aware that these factors might mean you are at increased risk for gestational diabetes can be good motivation to work on improving your diet or move more, and may help you avoid medication should you be diagnosed.

How Is it Diagnosed?

There are a few different ways to diagnose gestational diabetes. Not all providers are open to all methods, but it’s worth understanding the different options in case you’d like to explore something other than what is being offered. 

• Glucose tolerance test: This is the most common method in the United States to test for gestational diabetes. This is a two step process that starts with a 50-gram glucose challenge test. You do not have to be fasting for this first test, so eat a normal meal 2-3 hours beforehand; there are no “magical” meals that will help you to pass the test, but I recommend something filled with protein, fat, and fiber. You will be asked to drink a beverage (called Glucola), and after an hour your blood sugar is tested to see how your body could manage the large load of glucose. If you are above a certain threshold, you will move on to the second step, which is the 100-gram glucose tolerance test. For this test, it is required to be fasting, as your blood will be drawn before consuming the Glucola, and then at one, two, and three hours after. If you receive two elevated readings then you are presumed to have gestational diabetes. Keep in mind that it’s one drink at one point in time, and it only measures glucose, not insulin. Note, an alternative to Glucola, called the Fresh Test has become available. It is more appealing to many mamas as it contains just three simple ingredients and none of the questionable additives that are in Glucola. 
• Blood glucose monitoring: An alternative to the glucose tolerance test is blood glucose monitoring at home. This is essentially what you’d do to monitor blood sugar if diagnosed with gestational diabetes. Not all providers allow this approach, but it is quite informative and may be preferred by women who are wanting to avoid the Glucola drinks. With this method, you have the benefit of collecting more data points than with the glucose tolerance test, and those data points can be a more realistic representation of your body’s glucose control. However, the downside is that this process is time consuming and the supplies that you need to monitor are often an out of pocket expense. It's important to note that when you monitor your blood glucose for this test that you eat as you normally do. Restricting sugar or carbohydrates that you wouldn’t otherwise restrict won’t give you an accurate look at your blood sugar, and could result in a missed diagnosis. Unmanaged or undiagnosed gestational diabetes is far worse than managed, diagnosed gestational diabetes. 
• Early test: if you have other risk factors (like family history of diabetes or a personal history of PCOS), you may request a test that can provide an early indicator of gestational diabetes. This would allow you to start making dietary changes before the second trimester. This early test involves checking your hemoglobin A1C (average blood glucose level) during preconception and/or in the First Trimester. A result of 5.7% or greater would be a likely indicator of gestational diabetes.

What Are the Risks?

Gestational diabetes does come with additional risks to both mama and baby. However, managing blood sugar after diagnosis through diet and regular monitoring will help to decrease these risks:

• Increased risk of having a cesarean delivery 
• Increased risk of preeclampsia
• Increased risk of baby being born too large, thus possibly causing issues during a vaginal delivery such as shoulder dystocia, or increased tearing and bleeding for mom
• Increased risk of developing pre diabetes/type 2 diabetes in the future for both mom and baby
• Low blood sugar at birth for baby

It's also worth noting that gestational diabetes may push a mama into a “high risk” category. This can have implications like requiring additional monitoring or “risking out” of certain preferences - like birthing at birth center or home birth.

How Can it Be Managed?

If you do get a gestational diabetes diagnosis, know that it can often be managed successfully through lifestyle factors:

• Diet modifications: managing your blood sugar through diet is safe and effective in most cases. It also decreases the risk of macrosomia and can help mom achieve a healthy weight gain.
• Blood sugar monitoring: monitoring blood sugar provides you with the information you need to understand how different foods influence your blood sugar.
• Movement/exercise: staying active throughout pregnancy, through walking, Pilates, cycling, or strength training, helps immensely to manage blood sugar.
• Self-care: adequate sleep and stress-reduction are often overlooked but have a great impact on your blood sugar and overall health.

Conclusion

Gestational diabetes can seem like a scary and shameful diagnosis, but know that you are not alone, mama! If managed well you can go on to have a safe delivery and healthy baby. Working with a dietitian or diabetes educator, or finding a support group of other moms going through the GDM journey too, can make this hiccup in the third trimester even more manageable.