Final answer:
A teratogen is a chemical or agent that causes birth defects and includes substances like alcohol, cigarette smoke, and certain drugs and chemicals. Their impact depends on factors such as dosage, timing during pregnancy, and genetic susceptibility.
Step-by-step explanation:
A chemical or agent that causes birth defects is specifically called a teratogen. These are environmental agents, which can be biological, chemical, or physical, that cause damage to the developing embryo or fetus. Teratogens include substances such as alcohol, cigarettes, and certain prescription and illegal drugs, as well as environmental chemicals like pesticides and heavy metals. The effects of teratogens on fetal development vary depending on the potency of the teratogen, the duration of exposure, and when during development the exposure occurs.
Examples of teratogens include Thalidomide, alcohol, which can cause fetal alcohol spectrum disorders, and certain prescription drugs that can cause congenital abnormalities if consumed during pregnancy. It's important to note that not every exposure leads to birth defects; factors such as genetic susceptibility and dose also play significant roles.