teratogen

Teratology is the study of abnormal embryonic and fetal development. A teratogen is an agent that can cause developmental abnormalities, leading to structural or functional defects in the embryo or fetus. These defects can range from growth retardation and malformations to miscarriage or fetal death.

Teratogens can include physical agents like irradiation, chemical agents such as alcohol, drugs (e.g., thalidomide, phenytoin, diethylstilbestrol), and infections (e.g., chickenpox). Maternal hormonal deficiencies or excesses can also contribute to abnormal development.

The most critical period for teratogen exposure is the first trimester of pregnancy, as organogenesis is most vulnerable during this time. Exposure can occur through various mechanisms, including direct cell damage or indirectly by causing maternal toxicity that affects nutrient or oxygen supply to the embryo. The effects of teratogens can manifest as physical abnormalities, central nervous system dysfunction, or even transplacental carcinogenesis, leading to cancer in offspring after birth.12