Teratogen Health Article

Definition

A teratogen is any environmental influence that adversely affects the normal development of the fetus.

Description

Abnormal fetal development may result from exposure to a teratogen. There are four different teratogen categories: physical agents (radiation and hyperthermia), metabolic conditions affecting the mother, infection, and drugs (like thalidomide) and alcohol.

Physical agents

• Hyperthermia (fever, sauna)
• Ionizing radiation (x rays)

Hyperthermia

Women whose body temperature is raised while pregnant may have abnormalities result in their fetus. The rise in body temperature can be caused by infection or by spending time in hot areas such as a sauna or hot tub.

Ionizing radiation-mutagens versus teratogens

Any outside agent (like radiation) interfering with the process of development is considered a teratogen. Development is the process in which a tiny mass of undifferentiated cells (the embryo) multiplies and differentiates into the kidney, liver, heart, bone, muscles, and so on. Mutagens, however, are agents that directly affect and disrupt DNA, the genetic blueprint of an organism. Some agents, like radiation, are mutagens and teratogens. Ionizing radiation can cause defects either in development or it can damage DNA directly.

Metabolic disease

Infants of women with metabolic disorders have increased risks for abnormalities. Diabetic women, for example, are three to four times more likely to have fetuses with congenital abnormalities than infants of mothers without diabetes. The metabolic disease of the mother can have genetic or other causes.

Infection

There are a number of known infectious organisms which are teratogenic to the fetus, some of which cause damage directly, and some of which damage the fetus by causing a fever and raising the temperature of the mother.

Thalidomide

A dramatic example of a teratogen is thalidomide. In the early 1960s it was shown that more than 7,000 women who took the anti-nausea drug thalidomide during their pregnancy had children with very short or absent arms and legs. Other abnormalities were also seen in the children, such as the absence of ears, as well as heart and intestinal malformations. Affected infants were born to women who took thalidomide during the critical time period, also known as the period of susceptibility.