Diagnosis

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

If you're at high risk of diabetes — for example, if you're overweight or obese before pregnancy or you have a mother, father, sibling or child with diabetes — your doctor may test for diabetes early in pregnancy, likely at your first prenatal visit.

Routine screening for gestational diabetes

Screening tests may vary slightly depending on your health care provider, but generally include:

• Initial glucose challenge test. You'll drink a syrupy glucose solution. One hour later, you'll have a blood test to measure your blood sugar level. A blood sugar level of 190 milligrams per deciliter (mg/dL), or 10.6 millimoles per liter (mmol/L) indicates gestational diabetes.

  A blood sugar below 140 mg/dL (7.8 mmol/L) is usually considered normal on a glucose challenge test, although this may vary by clinic or lab. If your blood sugar level is higher than normal, you'll need another glucose tolerance test to determine if you have the condition.

• Follow-up glucose tolerance testing. This test is similar to the initial test — except the sweet solution will have even more sugar and your blood sugar will be checked every hour for three hours. If at least two of the blood sugar readings are higher than expected, you'll be diagnosed with gestational diabetes.