Information
One of the tests that every expectant mother should undergo during pregnancy is the oral glucose tolerance test (oGTT). The test is used to rule out gestational diabetes. The principle of the oGTT is to measure blood sugar levels (glycemia) on an empty stomach and then after ingesting a large amount of sugar, which is administered in the form of a special solution.
What is gestational diabetes
Gestational diabetes (gestational diabetes mellitus) is an elevated blood sugar level first detected during pregnancy. Carbohydrate metabolism disorders occur in up to 18% of women during pregnancy. It usually begins in the second half of pregnancy and, in the vast majority of cases, resolves after childbirth, at the latest within the postpartum period.
If gestational diabetes is detected and treated in time, the pregnancy and delivery proceed just as they would for women without diabetes. Untreated gestational diabetes carries an increased risk of complications during pregnancy and childbirth. For your baby, it means a lifelong increased risk of lifestyle-related diseases, such as obesity, type 2 diabetes, and cardiovascular disease.
How the testing is conducted
We perform the first blood sugar (glycemia) test as soon as possible after pregnancy is confirmed. At that stage, it is a non-stress test, meaning it involves only a blood sample taken on an empty stomach. We perform the actual oral glucose tolerance test (oGTT) between the 24th and 28th weeks of pregnancy for all women who did not have diabetes at the start of their pregnancy.
On the day of the test, we will draw blood while you are fasting and measure your blood glucose level. If the value is within the normal range, we proceed to the oral glucose tolerance test. If the value is higher even on an empty stomach, we repeat the blood draw on another day. If the blood glucose level is higher than 5.1 mmol/L on the second test as well, we confirm the diagnosis of gestational diabetes and will inform you of the next steps—first, you will need a consultation with a diabetes specialist.
If your fasting blood glucose is within the normal range, you will drink a solution containing 75 grams of glucose. To reduce the sweet taste, we use special solutions that contain citric acid. After drinking the solution, you will remain seated at rest, and over the next two hours, we will draw blood twice more to determine your glycemic curve.
How to prepare for an oGTT
You need to prepare for the test. The day before the test, eat as you normally would and do not restrict your carbohydrate intake. Avoid strenuous physical activity. You must fast for at least eight hours before the test, so stay on an empty stomach in the morning and drink only unsweetened beverages, ideally plain water. If you take any medications in the morning, postpone taking them until after the test is over. If you have a cold or are ill, do not undergo the oGTT and schedule a new appointment for when you are feeling better.
You are not allowed to eat or smoke during the test itself. If necessary, you may wash down the sweet solution with a little water. After the test is over, take your time to drink and eat, rest for a while in the clinic’s facilities, and only then go home. Your gynecologist will, of course, review and clarify all necessary information with you well in advance of the test date
