## **Core Concept**
The question revolves around the management of a pregnant woman diagnosed with major placenta previa at 28 weeks of gestation. Placenta previa is a condition where the placenta partially or completely covers the internal cervical os. The diagnosis is often made or suspected on ultrasound, and further evaluation is crucial for management.

## **Why the Correct Answer is Right**
A confirmatory scan for placenta previa is typically recommended after a certain period to assess for any changes in the placenta's position relative to the cervix, as well as to evaluate for any associated complications. Performing a scan too early might lead to unnecessary interventions, as some cases may resolve on their own as the uterus expands. The correct timing for a confirmatory scan in cases of suspected placenta previa, especially when detected at 28 weeks, usually involves waiting for a few weeks to allow for potential changes in uterine and placental anatomy.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because repeating the scan too soon (e.g., immediately) after the initial diagnosis might not provide additional useful information regarding changes in the placenta's position or potential resolution of the previa.
- **Option B:** This option suggests a very short interval, which might not be sufficient to observe significant changes in the placenta's position due to uterine growth.
- **Option C:** Although not explicitly incorrect without knowing the exact gestational age being referred to, this option does not match the correct answer based on standard practices.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in cases of placenta previa diagnosed in the second trimester, a follow-up ultrasound is often recommended at around 32-34 weeks of gestation. This timing allows for assessment of fetal growth and any changes in the previa's status before planning delivery, which is usually recommended around 36-37 weeks or earlier if there's significant bleeding.

## **Correct Answer:** .