Why it's done

The glucose challenge test is used to screen for gestational diabetes during pregnancy.

If you're at average risk of gestational diabetes, you'll likely be screened during your second trimester — between 24 and 28 weeks of pregnancy.

If you're at high risk of gestational diabetes, your health care provider may recommend doing the screening as early as your first prenatal visit. Risk factors may include:

• Being or having a body mass index of 30 or higher (obesity).
• A lack of physical activity.
• Gestational diabetes in an earlier pregnancy.
• Having a medical condition associated with the development of diabetes, such as metabolic syndrome or polycystic ovary syndrome.
• Diabetes in a blood relative.
• Previously delivering a baby weighing more than 9 pounds (4.1 kilograms).
• Race and ethnicity — Women who are Black, Hispanic, American Indian and Asian American have a higher risk of developing gestational diabetes.

Most women who have gestational diabetes deliver healthy babies. However, without careful management, gestational diabetes can lead to pregnancy complications such as a serious condition that causes high blood pressure and other symptoms that can threaten the lives of both mother and baby (preeclampsia). Gestational diabetes can also increase your risk of having a baby with an excessive birth weight — which might increase the risk of birth injuries or prompt a C-section delivery.

Women who've had gestational diabetes also have a higher risk of getting type 2 diabetes.