When and how is gestational diabetes screened?

• A. Screen at 24-28 weeks with a 1-hour 50 g glucose challenge test; if abnormal, perform a 3-hour 100 g OGTT.
• B. Screen at first prenatal visit with a 75 g OGTT.
• C. Screen only if obesity.
• D. Screen after delivery.

Answer: (A)

Gestational diabetes screening uses a two-step process in the late second trimester. At 24–28 weeks, all or most pregnant individuals undergo a nonfasting 50 g glucose challenge test. If the 1-hour plasma glucose after that challenge is above the threshold (commonly around 130–140 mg/dL), a diagnostic 3-hour 100 g OGTT is performed to confirm gestational diabetes using established criteria (Carpenter-Coustan or NDDG). This approach balances ease of screening with accuracy, ensuring those with glucose intolerance are identified while avoiding unnecessary testing in everyone. Screening at the first prenatal visit or only based on obesity isn’t the standard universal strategy, and screening after delivery doesn’t assess ongoing pregnancy.