Why does your provider recommend glucose testing in pregnancy and how is the test performed?
Glucose testing is recommended for all women in pregnancy between 24-28 weeks’ gestation. There are some risk factors where screening may be needed earlier. These include a personal or family history diabetes, elevated pre-pregnancy BMI, age 35 or older, or PCOS. Gestational diabetes can affect up to 10% of pregnant women. Undiagnosed gestational diabetes can result in poor outcomes for mothers and their infants. To prevent these poor outcomes, screening is done on all pregnant women. If a diagnosis of diabetes is made extra monitoring, including more prenatal visits, is needed through the rest of the pregnancy.
The first test is a screening test. If the first test is elevated then a second, diagnostic test is ordered. If the first test is normal then no further testing is needed. The initial screening test consists of drinking a 50-gram dose of dextrose (sugar) quickly, in five minutes or less. Then, a blood draw for a blood sugar level is performed one hour later. 50 grams of sugar is like drinking 14oz of cranberry juice or 16oz of a regular soda (although these are not good testing alternatives – we'll talk about why below). The test is not fasting, meaning you can eat that day. Although, it is recommended to not eat anything two hours beforehand to ensure testing accuracy.
We get a lot of questions about what is in the drink itself. The ingredients are dextrose (not high fructose corn syrup), citric acid, water, sodium benzoate, artificial flavors, and food dye if the drink has coloring (not all flavors do). The drink is considered safe in pregnancy with no known negative side effects for the infant. The drink can cause some nausea or dizziness but that is not common. It is like drinking a flat soda or extra sugary Gatorade. There is an alternative testing option. The Fresh Test can be used if women prefer an organic option. It can be purchased online. However, other alternative options such as juice or soda, are not considered accurate because they are made with fructose, not dextrose, which is processed differently by the body.
If your initial screening test is elevated, a second test will be recommended. It is a three-hour diagnostic test which should be completed as soon as possible to ensure we are diagnosing and treating diabetes if it is present. The three-hour test is fasting, which means nothing to eat or drink for at least eight hours beforehand. Blood is drawn before drinking the drink and one, two, and three hours afterwards. The drink also consists of more dextrose (sugar), 100 grams. It is common for women to experience more nausea with this test since it is performed while fasting. If two of the four lab values are elevated, then the diabetes diagnosis is made. A specialized plan of care will then be made for each mother. This plan will involve input from the entire obstetric team including diabetes specialists. All women with diabetes should check their blood sugars several times a day and keep track of them to show their provider at their prenatal appointments.
