Final answer:
Nicotine and rubella are considered teratogens, which are substances that can cause developmental issues or birth defects in an embryo or fetus. They can include drugs, chemicals, and viruses, with severity depending on exposure timing and levels.
Step-by-step explanation:
Nicotine and rubella are examples of teratogens. Teratogens are substances or factors that can cause congenital defects or developmental malformations in embryos or fetuses. Teratogens include a variety of different types of compounds and conditions such as illicit drugs like heroin and cocaine, prescription and over-the-counter medications, certain viruses, exposure to radiation, and substance abuse including smoking due to compounds like nicotine. In the case of rubella, it is a virus that can affect pregnant women, leading to serious birth defects if the infection occurs during pregnancy. Nicotine, on the other hand, is a chemical compound found in tobacco that can be detrimental to fetal development when a mother smokes during pregnancy.
Birth defects associated with teratogen exposure can range from physical malformations to developmental delays and can depend on factors like the timing and level of exposure. It's crucial for pregnant women to avoid known teratogens to safeguard against these risks.