Teratogeny

Teratogeny, or teratogenicity, refers to the capacity of an agent to cause developmental abnormalities in an embryo or fetus. Teratogens can produce congenital malformations, growth restriction, or functional impairments, depending on the timing of exposure, the dose, and the genetic makeup of the mother and fetus. Most sensitive periods are during organ formation in early pregnancy, but later exposures can still affect development. Risk is influenced by maternal health, nutrition, and concurrent exposures.

Common categories and examples include drugs with teratogenic potential such as isotretinoin, thalidomide, valproic acid, phenytoin, methotrexate, and warfarin; some others such as ACE inhibitors and lithium carry elevated risks. Infections such as rubella, cytomegalovirus, toxoplasmosis, and Zika virus, as well as environmental exposures like alcohol (fetal alcohol spectrum disorders) and radiation, can act as teratogens. Diabetes in pregnancy and folate deficiency are risk modifiers rather than teratogens themselves.

Prevention and management involve avoidance of known teratogens, vaccination when applicable, careful medication use during pregnancy with risk-benefit assessment, and folic acid supplementation to reduce certain neural tube defects. Early prenatal care and screening help detect anomalies. Teratogenic risks are evaluated using animal and human data; regulatory agencies historically used classification schemes to guide labeling, with emphasis on informed decision-making.

The study of teratogens and birth defects is teratology; notable historical episodes include thalidomide-induced limb defects and the DES tragedy, which underscored the need for rigorous drug testing and surveillance.