A teratogen is defined as an agent that causes permanent alterations
in the form or function of offspring upon exposure to
the fetus (Table 2).43,44 There is a wide range of medications
that can lead to teratogenic effects and thus can be a reason
to cause both functional and structural birth defects. Potential
teratogenic medications include alcohol, tobacco, cocaine,
thalidomide, methyl mercury, anticonvulsant medications,
warfarin compounds, ACE inhibitors, certain antimicrobials,
retinoids, penicillamine tetracycline, trimethadione, valproic
acid and phenytoin. The period that is considered to be most
prone to teratogens is the embryonic period (first trimester).
However, teratogen exposure does not harm much after
development of venerable structures with the exception of
tetracycline that may cause yellow brown discoloration of
deciduous teeth even during the second half of pregnancy