Birth defects (BD) is a consensus political term for malformations and functional disorders (“mental retardation and disorders” are most common and burdensome to parents, family and society); noted at any age (many BD are detected years after birth), of familial or sporadic nature (most BD are not familial) whose cause was present at birth (genetic or teratogenic).

Modern Teratology can be said to have begun “ in the 1940’s when Josef Warkany and his associates fist forcefully called attention to the fact that environmental factors such as maternal dietary deficiencies and X-irradiation could adversely affect intrauterine development in mammals. “

“At present (1977), six teratological generalizations are sufficiently well defined to justify being called principles.”

Thalidimide Embryopathy

1 – Susceptibility to teratogenesis depends on the genotype of the conceptus (and the mother) and the manner in which they interact with environmental factors.

2 – Susceptibility to teatogens varies with the developmental stage at the time of exposure.

3 – Teratogens (etiology) act in specific ways (mechanisms) conducive to a recognizable pathogenesis  (mutation, chromosome damage, mitotic disruption, enzymatic alteration or inhibition, etc., producing enhanced or reduced cell death or apoptosis, etc.) impacting specific cells which in turn may be causative of clinically recognizable phenotypes or syndromes (functional or structural malformations or birth defects, a subject studied by dysmorphologists)  (toxic agents have uncharacteristic or general non-specific embryonic-fetal effects).

4 – The “final” manifestations (phenotype) range from death to malformation, growth alterations (size, proportions and symmetry) and functional disorders. 

5 – The nature of the teratogen determines the extent that it can reach the embryo/fetus (Note: alcohol is water soluble and will cross the placenta and reach all the tissues of the embryo-fetus as well as breast milk). Small particles (less than 600 mol. Wt.) easily cross the placenta by simple diffusion.

6 – As dosage of exposure increases so do the deviant developmental effects on the developing embryo/fetus (dose response effects) (Note: many human tissue/organs continue to develop after birth).

For medical summaries more in:

http://www.ibis-birthdefects.org/start/drophealth.htm

For etymology and root ideas concerning Teratos, Teratoma, etc., more in:

http://www.consultsos.com/pandora/teratoge.htm