Who: All pregnant women.

Why: To check for gestational diabetes (diabetes during pregnancy).

When: Between 24 and 28 weeks of pregnancy.

How: The health care provider takes a blood sample one hour after the woman consumes a drink containing 50 grams of glucose (a form of sugar). If the screening test shows high blood sugar levels, the woman will need to take a diagnostic test to find out if she has gestational diabetes. The diagnostic test is three hours long.

Risks: None, except possible bruising or soreness at the needle site.