Which term describes substances that can cause birth defects if exposure occurs during pregnancy?

• A. Embryology
• B. Teratology
• C. Teratogenicity
• D. Teratogens

Answer: (D)

Teratogens are substances that can cause birth defects when exposure occurs during pregnancy. They are the agents that disrupt fetal development at sensitive times, leading to structural or functional abnormalities. Teratogenicity describes the capacity of something to cause such effects—the potential—whereas teratology is the field that studies birth defects. Embryology, by contrast, is the study of embryo development, not the agents that cause defects. So the term that names the substances themselves is teratogens.