What is a teratogen?

A teratogen is defined as a substance or factor that causes malformation or developmental issues in a fetus during pregnancy. When a pregnant individual is exposed to teratogens, these substances can interfere with normal fetal development, leading to birth defects or other health complications for the baby. Examples of known teratogens include certain medications, alcohol, and infectious agents.

The other options refer to different categories of harmful substances. A substance that triggers allergic reactions primarily affects the immune system rather than fetal development. A carcinogenic chemical is specifically related to cancer development, while a respiratory irritant affects the respiratory system. While these substances can certainly pose significant health risks, their mechanisms of action and the outcomes they produce are distinct from those of teratogens. Thus, the correct identification of a teratogen as a substance that damages the fetus aligns accurately with the established definitions in the field of maternal and fetal health.