Second Trimester Tests

Content Provided by March of Dimes

Most women are screened for gestational diabetes between the 24th and 28th week of pregnancy. Women who are considered at high risk (including women who have had gestational diabetes in a previous pregnancy) often are screened at an early prenatal visit. If test results are normal, they are screened again at 24 to 28 weeks.

The test involves drinking a liquid that contains 50 grams of glucose (a form of sugar). One hour later, the health care provider takes a blood sample. The sample is sent to the lab to measure the amount of glucose in the blood.

If the screening test shows that a woman has high levels of glucose in her blood, she needs to take a similar, though longer, test called the glucose tolerance test. It involves drawing blood samples while fasting and at 1, 2 and 3 hours after drinking 100 grams of glucose.

Most women diagnosed with gestational diabetes can control their blood-sugar levels with diet and exercise.