Teratogens are defined as which of the following?

• A. Teratogens are nutrients essential for fetal growth.
• B. Teratogens are genetic mutations always present.
• C. Teratogens are environmental factors with no effect.
• D. Teratogens are defined as agents that can disrupt fetal development.

Answer: (D)

Teratogens are factors that have the potential to disrupt fetal development when a pregnant person is exposed, especially during critical windows of organ formation. They include chemicals, drugs, infections, radiation, and certain maternal conditions. This explanation fits best because teratogens are defined by their capacity to interfere with normal fetal growth and cause birth defects or developmental problems, rather than being nutrients the fetus needs or inherent genetic mutations. Some exposures may have little or no effect depending on timing or dose, but the defining idea is their ability to cause disruption. Examples help anchor the concept: alcohol can cause fetal alcohol spectrum disorders, isotretinoin can lead to craniofacial and limb defects, rubella can cause congenital anomalies, and various medications or environmental factors can pose risks.