## **Core Concept**
Ebstein's anomaly is a congenital heart defect characterized by the abnormal formation of the tricuspid valve and the right ventricle. It is associated with maternal exposure to certain substances during pregnancy. The anomaly involves a downward displacement of the tricuspid valve into the right ventricle, leading to a small right ventricle and an enlarged right atrium.

## **Why the Correct Answer is Right**
Lithium is known to be associated with Ebstein's anomaly when taken by pregnant women, particularly during the first trimester. The exact mechanism is not fully understood, but lithium exposure has been linked to an increased risk of cardiac malformations, including Ebstein's anomaly, in the developing fetus. The risk is still relatively low, but it is a significant concern due to the severity of the anomaly.

## **Why Each Wrong Option is Incorrect**
* **Option A:** There is no well-established link between this option and Ebstein's anomaly.
* **Option B:** Similarly, there is no established association with Ebstein's anomaly.
* **Option D:** This option is also not linked to Ebstein's anomaly.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that while the risk of Ebstein's anomaly with lithium exposure is increased, it is still very low. The absolute risk is approximately 1 in 1,000. Pregnant women taking lithium should be closely monitored, and the decision to continue or discontinue lithium should be made on a case-by-case basis, considering the risks and benefits.

## **Correct Answer:** . Lithium