Gestational diabetes - glucose intolerance of pregnancy

Gestational diabetes (also called glucose intolerance of pregnancy) is a temporary condition that occurs during pregnancy. It affects two to four per cent of all pregnancies and involves an increased risk of developing diabetes for both mother and child.

Screening and diagnosis

Your doctor may not screen you for gestational diabetes if you're younger than 25 and have no other risk factors for the disorder. Otherwise, you may be screened using a glucose challenge test. The test is usually done between 24 and 28 weeks of pregnancy, although it may be performed earlier if your doctor thinks you're especially at risk.

There's no special preparation for this test, but you do need to fast for six hours beforehand. On the day of the test, you'll be asked to drink a glucose solution. An hour later, blood is drawn from a vein in your arm, and your blood sugar level is checked.

Although the amount of sugar in your blood fluctuates, the range is relatively narrow. After fasting all night, most people have levels between 70 and 110 milligrams of glucose per deciliter of blood (mg/dL). That's the equivalent of about 1 teaspoon of sugar in a gallon of water. But your blood sugar levels rise considerably after a meal, especially one high in sugar. A blood sugar level below 140 mg/dL is considered normal on a fasting glucose challenge test.

Having a blood sugar level above 140 mg/dL doesn't necessarily mean you have gestational diabetes. To confirm the diagnosis, a second test is necessary.

For the follow-up test, you'll be asked to fast overnight. You're then given another solution to drink — this one containing a higher concentration of glucose — and your blood sugar levels are checked every hour for a period of three hours. Having at least two instances of abnormally high blood sugar levels confirms the diagnosis of gestational diabetes.