What is the common characteristic of a medication classified under category 'X' by the FDA?

Medications classified under category 'X' by the FDA are recognized for having a definitive risk of causing fetal abnormalities. This classification indicates that the evidence of harm to the fetus is conclusive, and the use of such medications in pregnancy is contraindicated. This means that the potential risks to the fetus outweigh any potential benefits of using the medication for the mother.

The category also emphasizes the necessity of avoiding these medications during pregnancy, as they can significantly impact fetal development regardless of the stage of pregnancy. This helps healthcare providers identify which medications should not be prescribed to pregnant patients to safeguard fetal health.

Other classifications, such as 'A', 'B', 'C', and 'D', suggest varying levels of risk; for instance, category 'A' medications are considered safe, while category 'D' has been associated with certain risks. However, category 'X' is the most severe in terms of risk, clearly indicating that no circumstances justify its use during pregnancy.