What to know about screening for gestational diabetes

by Kaiser Permanente |
A pregnant woman with a blood sugar sensor on her hand pours lemon juice into a glass.

High blood sugar that occurs only while you are pregnant is known as gestational diabetes.

Why screen for gestational diabetes?

Gestational diabetes affects how your cells use sugar, or glucose. It is important to know whether you have gestational diabetes because having high blood sugar can affect your pregnancy and your baby's health.

Gestational diabetes can affect the health of both you and your baby by:

  • Making premature birth more likely.
  • Causing your baby to be larger (9 pounds or more). This can affect the birthing process and make a cesarean birth (C-section) more likely.
  • Putting you at higher risk of having type 2 diabetes later in life.
  • Raising your risk of having high blood pressure or preeclampsia.

Screening tests for gestational diabetes

Screening for gestational diabetes shows whether your blood sugar is too high. These screenings are usually done between 24 and 28 weeks of pregnancy.

Blood sugar is usually measured first with a one-part test. If this test is abnormal, your clinician will recommend that you do a two-part glucose tolerance test.

For the one-part test, you will be given a sugary drink. An hour later, the lab will test your blood to check your blood sugar level. If your blood sugar is below 140 mg/dL, you have tested negative for gestational diabetes. If your blood sugar is higher than 140 mg/dL, you’ll probably follow up with the two-part screening test. This is usually scheduled for a different day because you’ll need to fast for at least 8 hours.

In the two-part test, you’ll have your blood drawn to check your fasting blood sugar level. Then you’ll be given a sugary drink and have your blood sugar checked again after 1 hour, after 2 hours, and sometimes also after 3 hours. Your clinician will discuss the results of this test and whether it shows you are positive for gestational diabetes.

Risks of screening

Most people have no problems with these screening, but occasionally blood sugar levels drop to very low levels near the end of the test. If this happens, you could have symptoms like fatigue, hunger, or feeling shaky. It’s important to let your clinician know if you experience any of these symptoms.

In rare cases, people vomit after drinking the sugary liquid. If this happens, your clinician may reschedule the test.

What does it mean to screen positive for gestational diabetes?

Having high blood sugar during pregnancy can be managed by eating healthy foods, exercising, and, if necessary, taking medication. Controlling blood sugar can keep you and your baby healthy and prevent a difficult birth.

To keep track of your blood sugar levels, your care team will want to monitor you more regularly. This will likely involve receiving a home glucose testing kit so you can monitor your levels at home. Your care team will discuss what options are available to you.

If you have gestational diabetes during pregnancy, your blood sugar usually returns to its usual level soon after birth. If you've had gestational diabetes, you have a higher risk of getting type 2 diabetes. You'll need to be tested more often for changes in blood sugar.

Reducing your risk of gestational diabetes

Adopting healthy habits before and during pregnancy can help prevent gestational diabetes. These include:

  • Eating healthy foods. Choose foods high in fiber and low in fat and calories. Focus on eating a variety of fruits, vegetables, and whole grains. Pay attention to portion size.
  • Staying active. Aim for 30 minutes of moderate activity most days of the week. Take a brisk daily walk. Ride your bike. Swim laps. Short bursts of activity — such as parking further away from the store when you run errands — add up.
  • Don't gain more weight than recommended. Gaining some weight during pregnancy is healthy, but gaining too much weight too quickly can increase your risk of gestational diabetes. Talk to your clinician if you have any questions about what a reasonable amount of weight gain is for you.

If you've had gestational diabetes, these healthy choices may also reduce your risk of having it again during future pregnancies or developing type 2 diabetes later in life.

This article has been created by a national group of Kaiser Permanente ob-gyns, certified nurse-midwives, pediatricians, lactation consultants and other specialists who came together to provide you with the best pregnancy, birth, postpartum, and newborn information.

Some of the content is used and adapted with permission of The Permanente Medical Group.