## **Core Concept**
Gestational diabetes mellitus (GDM) is a condition characterized by high blood sugar levels that are first recognized during pregnancy. The screening for GDM is crucial for early detection and management to prevent complications for both the mother and the fetus. The timing of screening is important for effective management.

## **Why the Correct Answer is Right**
The correct approach for screening gestational diabetes involves testing between **24 to 28 weeks of gestation**. This period is chosen because it usually coincides with the time when insulin resistance becomes more pronounced due to the increasing levels of placental hormones. Early detection allows for interventions that can reduce the risk of complications.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Screening before 24 weeks may be considered for high-risk women, but it's not the standard timing for general screening.
- **Option B:** Although some guidelines suggest testing at 24-28 weeks, option A (before 24 weeks) and option C (after 28 weeks) are less optimal for routine screening.
- **Option D:** Screening at term or very close to it (option C) is too late for interventions to significantly impact outcomes.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the American College of Obstetricians and Gynecologists (ACOG) and other organizations recommend a **2-step approach** for screening GDM, which typically involves an initial glucose challenge test (GCT) followed by a diagnostic oral glucose tolerance test (OGTT) for those who screen positive. The timing of **24-28 weeks** is critical for this process.

## **Correct Answer:** B. 24-28 weeks.