## Core Concept
The categorization of drugs during pregnancy is crucial for guiding clinicians in prescribing medications to pregnant women. The U.S. Food and Drug Administration (FDA) classifies drugs based on their potential risks to the fetus. Category X drugs are those that have shown positive evidence of human fetal risk, such that the risks in pregnant women are not acceptable.

## Why the Correct Answer is Right
Category X drugs are contraindicated in pregnancy due to the high risk of fetal harm or death. These drugs have demonstrated teratogenic effects or other adverse outcomes in human studies. The correct answer, , is a category X drug, implying it has been associated with significant fetal risk.

## Why Each Wrong Option is Incorrect
* **Option A:** is not classified as a category X drug, suggesting it has a lower risk profile or is used under specific circumstances where benefits outweigh risks.
* **Option B:** does not fall into category X, possibly indicating it has some safety data supporting its use or it requires careful consideration but isn't absolutely contraindicated.
* **Option C:** is not a category X drug, which could mean it has less severe risks or there's limited data suggesting it's safer than category X drugs.

## Clinical Pearl / High-Yield Fact
A key point to remember is that category X drugs are absolutely contraindicated in pregnancy. Clinicians must carefully evaluate the risks and benefits of any medication prescribed to pregnant women, avoiding category X drugs whenever possible.

## Correct Answer Line
**Correct Answer: D. **