a class of environmental hazards which cause marked abnormalities in the fetus during pre-natal development and which are can be caused by the use of harmful drugs or substances, such as thalidomide and cocaine, cigarette smoking and heavy use of alcohol.

agents that cause anomalies or malformations during embryological development.

Agents that cause physical defects in a developing fetus

Agents that cause congenital defects in a developing embryo or fetus.

Substances that cause malformation or serious deviation from normal development of embryos and fetuses.()

Any agent that raises the incidence of congenital malformations.

any substance that can cause a birth defect.

Agents such as drugs, chemicals and infections that can cause birth defects when a mother is exposed to them during pregnancy.