Teratogens

What is the mechanism of teratogenic action?
What are teratogenic agents? 

The most dangerous effect of exposure to a toxic substance occurs when it impacts fetal development and the birth of a child. At birth, the number of children identified as having either a major or minor malformation is approximately 5 percent. Toxic agents that cause abnormal development resulting in birth defects are referred to teratogens.

Mechanisms of action
Birth defects may be associated with mechanisms such as mutation, chromosomal damage, mitotic interference, altered nucleic acid integrity and/or function, altered energy sources, changes in cell membrane characteristics and enzyme inhibition. Birth defects are most likely to occur if exposure takes place during organ development. The type and severity of birth defect that occurs is often dependent on the time of exposure and the toxic agent involved. Manifestations of exposure may appear as physical malformations, growth impairment, death of the developing embryo/fetus (miscarriage), or functional impairment of organs. Several mechanisms by which teratogenic substances may cause their effect include cell death, genotoxicity, impaired cell function, maternal toxicity and placental toxicity.

Teratogenic agents
Several teratogenic agents are radiation, metals and solvents, Thalidomide, diethylstilbestrol, ethanol and cocaine.

Reference:
Kent, C. 1998. Basics of Toxicology. John Wiley & Sons, Inc. New York