What is defined as a teratogen?

A teratogen is specifically defined as a substance that can cause birth defects in a developing fetus when the fetus is exposed to it during pregnancy. This definition focuses on the harmful effects that certain agents can have on fetal development, leading to structural or functional abnormalities that may affect the infant's health after birth.

The term encompasses a wide range of substances, including certain drugs, chemicals, infections, and even environmental factors. The critical aspect of teratogens is their ability to disrupt normal fetal development, potentially leading to congenital anomalies.

In contrast, the other options describe substances that either have no harmful effects on fetuses or are specifically beneficial or targeted to adults. For example, a substance deemed harmless to fetuses would not qualify as a teratogen since it does not pose any risk of causing birth defects. Similarly, a substance that only affects adults would fall outside the scope of teratogenic risk, as it does not involve fetal exposure. Lastly, a chemical considered beneficial during pregnancy would typically be one prescribed to support fetal health, further disqualifying it from being classified as a teratogen. Understanding the implications of exposure to teratogens is crucial for ensuring the health and safety of both the mother and the developing fetus.