Final answer:
Teratogens are environmental agents that can cause damage to the developing fetus. Examples of teratogens include drugs, alcohol, viruses, and chemicals. These substances can permanently deform the structure or function of a fetus.
Step-by-step explanation:
A teratogen is any environmental agent-biological, chemical, or physical-that causes damage to the developing embryo or fetus. Teratogens include various drugs, chemical compounds, alcohol, and viruses. Examples of teratogens are heroin, cocaine, methamphetamine, prescription medicines, alcohol, viruses like HIV and herpes, and rubella. These substances can permanently deform the structure or function of a developing fetus in utero.