Exams and Tests
Almost all women are tested for gestational diabetes between the 24th and 28th weeks of pregnancy. If your doctor thinks you are at increased risk for developing gestational diabetes, you may be tested earlier.
Gestational diabetes is diagnosed with an oral glucose tolerance test. Your blood sugar is tested 1 hour after you drink a small cup of a sweet liquid. If your results from this test come back high, you will need to do a second test—a longer, 3-hour glucose test. In this test, you cannot eat or drink anything except water for at least 8 hours. After fasting, your blood sugar level will be tested. Then you will drink a small cup of sweet liquid and have your blood sugar tested every hour for at least 3 hours. If your blood sugar levels come back high on two or more of these tests, you have gestational diabetes.
Tests during pregnancy
If you have gestational diabetes, your doctor will check your blood pressure at every visit. You will also have certain tests throughout your pregnancy to check your and your baby's health. These tests include:
- Home blood sugar monitoring. Testing your blood sugar at home every day helps you know if your blood sugar level is within a safe range.
- Gestational diabetes: Checking your blood sugar
- Fetal ultrasound. This test may be used to see if you need insulin or to estimate the age, weight, and health of your baby. The ultrasound test also can measure the size of your baby's abdomen, and this measurement along with other information can be used to help your doctor decide on your care. If your doctor thinks your baby is bigger than normal for his or her gestational age, then your doctor may decide you need to start taking insulin. Taking insulin when you have gestational diabetes will stop your baby from growing too big. Keep in mind that ultrasounds cannot always accurately estimate how much your baby weighs or whether there are other problems.
- Nonstress test. A nonstress test can help you know how well your baby is doing by checking your baby's heartbeat in response to movement.
Some doctors may recommend you have a hemoglobin A1c (glycosylated hemoglobin) or a similar test every month during your pregnancy. The A1c test estimates your average blood sugar level over the previous weeks to months.
Tests during labor and delivery
During labor and delivery, you and your baby will be monitored very closely.
- Fetal heart monitoring is used to see how well your baby is doing while you are in labor.
- Blood sugar tests are done at least every hour to make sure your blood sugar level is within a safe range.
Tests after delivery
After your baby is born, your blood sugar level will be checked several times. Your baby's blood sugar level will also be checked several times within the first few hours after birth. One to 3 days after delivery, you will have a fasting or random OGTT.
Most likely, your gestational diabetes will go away after your baby is born. But because you are at risk for developing type 2 diabetes, you should have a glucose tolerance test about 6 weeks after delivery and a fasting blood sugar level at least once a year. Your doctor may recommend that you have additional glucose tolerance testing if your fasting blood glucose levels are normal, or only slightly elevated.
The first time you see your doctor after you become pregnant, your doctor will determine your risk for gestational diabetes. If you are considered high risk because you have had gestational diabetes before, are obese, have a strong family history of type 2 diabetes, or have sugar in your urine, you will be tested right away.
Most women are tested between the 24th and 28th weeks of pregnancy. But you may not benefit from testing if:
- You are younger than 25 when you become pregnant.
- You have not had gestational diabetes before.
- You have no family history of type 2 diabetes.
- Your body mass index [BMI] is less than 25.
- You are not a member of a racial/ethnic group that has a high risk of developing diabetes, such as Latin Americans, Native Americans, Asian Americans, African Americans, or Pacific Islanders.
- You do not have polycystic ovary syndrome.
Some pregnant women are at low risk for developing gestational diabetes and may not need to be tested. Experts debate whether all pregnant women need to be tested for gestational diabetes. The U.S Preventive Services Task Force has found insufficient evidence to recommend screening women with no risk factors for gestational diabetes.3 But most doctors routinely test all pregnant women who are in their care.
Even though your gestational diabetes will probably go away after your baby is born, you are at risk for developing gestational diabetes again and for developing type 2 diabetes later in life. More than half of women who develop gestational diabetes will develop type 2 diabetes later in life.2
To make sure your blood sugar level stays within a safe range, your doctor may instruct you to continue checking your blood sugar levels at home for a while. You will also have a follow-up glucose tolerance test 6 to 12 weeks after your baby is born or after you stop breast-feeding your baby. If the results of this test are normal, you will still need to have a fasting blood sugar test at least every 3 years. Even if your sugar level is normal, you are at increased risk of developing diabetes in the future. Eating a healthy diet and getting regular exercise can help prevent type 2 diabetes.
Women who had gestational diabetes and use progestin-only birth control pills may have a greater chance of developing type 2 diabetes. Combination birth control pills that contain estrogen and progestin are not linked with an increased risk of type 2 diabetes. Talk to your doctor about the best kind of contraception for you.4
If you want to get pregnant again, you should be tested for diabetes both before you become pregnant and early in your pregnancy.