Teratogen

A developing embryo is far more sensitive than an adult. The same dose that causes no symptoms in the mother may harm the child, and the type of damage depends on which organs are forming when the exposure happens. Exposure in the first weeks, often before pregnancy is known, can be especially important.

The term describes a developmental effect, which is one part of the broader GHS class called reproductive toxicity. That class covers effects on sexual function and fertility, effects on development of offspring, and effects passed through breast milk. Teratogenicity falls in the development part, alongside outcomes such as growth changes or fetal loss.

Classification into Category 1A, 1B or 2 reflects how strong the evidence is. Human evidence leads to 1A, animal evidence to 1B, and weaker or limited evidence to 2. A teratogen is not the same as a Mutagen, because the harm comes from disrupted development rather than inherited gene changes.

Employers should handle this hazard through general controls that protect everyone, rather than assuming only some workers are at risk. Reproductive harm can also involve fathers, so controls should not rest on assumptions about who is exposed.