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.
• 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.