Teratogens are any agents or conditions which can harm prenatal development and lead to birth defects or even death of the fetus. They include viruses, drugs, chemicals, stressors, and malnutrition and other hazards that cause harmful environmental conditions for the developing fetus (James, 1973).

There are other teratogens that are referred to as behavioral teratogens. They harm the fetus’ brain and nervous system and affect the emotional and intellectual functioning of the child in future.

Although all teratogens increase the risk of harm to the developing child, none always cause damage. The final impact depends on the composite interaction of many factors as discussed below.

Timing of the teratogen is one factor promoting the effects of a teratogen on the developing organism depending on the stage and age of the pregnancy during which the child is exposed to it. Some teratogens cause damage only during specific days or weeks in early pregnancy while others cause at any time of the pregnancy.( Jones, 1973)

The frequency with which teratogens are exposed to the developing organism and amount of the teratogen also influences the impact on the fetus.

Genetic variability of the developing organism is another factor that determines whether a particular teratogen will be harmful to it. Having and lacking certain genes may make the developing child more vulnerable to the effect of a teratogen.

A good example of a teratogen is a maternal disease such as rubella, a viral disease that can harm a fetus if contracted during early pregnancy. It causes deafness, blindness and harm to the central nervous system of the fetus.

Social drugs like alcohol or marijuana are teratogens too. Alcohol causes abnormal facial features, slow physical development, and stunted mental progress after birth (James, 1973).

References

James G. Wilson (1973). Environment and Birth Defects (Environmental Science Series). London: Academic Pr.

Jones K.L., Smith D.W, Ulleland C.N., Streissguth A.P. (1973). “Pattern of malformation in offspring of chronic alcoholic mothers”. Lancet