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"It really is like a teratogen in pregnancy, a factor which interferes with normal fetal development, but it's still not taken seriously by a lot of medical professionals," Fejzo says.

Thalidomide, a well-known teratogen in humans, and retinoid derivatives -- used in treatments against leukaemia, psoriasis, and acne -- are known to cause severe heart defects in the fetus.

Potential teratogens are typically screened for using animals such as rodents and rabbits.

Initially, the courts concerned themselves with a narrow set of questions: Was Bendectin a teratogen?

Alcohol was a teratogen, a substance that kills or damages developing cells, the researchers said, and then for the first time used term fetal alcohol syndrome to describe the result.