Teratogenicity is the structural or functional dysgenesis of the foetal organs or creation of birth defects by drugs. The susceptibility to teratogenesis depends on the genotype of the foetus and varies with the developmental stage in which the exposure occurs.
The teratogenic effects can be lethal (spontaneous abortion, foetal death) or cause serious malformations. Retardation of growth and functional deficits are other manifestations of teratogens.
The mechanisms of teratogenicity are also at the molecular level. Teratogens can interfere in essential metabolic pathways, but they can also cause birth defects by DNA linking and subsequent mutagenesis.
For further information on teratogenicity you are referred to the section in Pregnancy & Teratogenicity.