Teratogenicity is the ability to cause developmental anomalies in a fetus. Things that can cause developmental abnormalities are known as teratogens, and they include things like viruses, chemicals, and radiation. Their study is known as teratology; all of these words share a Greek root meaning “monster,” a reference to the fact that some developmental abnormalities were viewed as monstrosities or marvels historically.
Substances with teratogenic effects can damage the DNA of a developing fetus. They may cause anything from abnormal development of a limb to malformation of an organ, and the effects for the developing fetus can vary depending on the teratogen, the gestational age of the fetus, and other factors. Sometimes, prenatal exposure to teratogenic substances causes the death of the fetus, while in other instances, someone may be born with relatively mild anomalies like extra fingers or toes.
Substances with known teratogenicity must be handled carefully. Pregnant women are encouraged to avoid exposure to such substances, and they are tightly controlled to minimize the risk of inadvertent release. As researchers have learned, however, sometimes the danger of a substance is not known until it is too late. Thalidomide, for example, was widely used in pregnant women until medical experts realized that it was causing developmental abnormalities.
It is difficult to study this topic in humans because there are serious ethical issues involved with exposing pregnant women to substances that might cause birth defects. As a result, the dosage at which substances become harmful is often not known because healthcare professionals do not want to expose women to various dosages in a controlled experiment to see which of them had babies with developmental abnormalities. As illustrated by thalidomide, which was used in lab animals safely, animal testing does not always categorically demonstrate that a substance is safe to use in pregnant women.
Pregnant women are usually told to avoid substances of unknown teratogenicity. Sometimes, medical professionals have reason to believe that a substance is probably harmful because it is related to other harmful compounds or because a link between exposure and developmental abnormalities has been noted. In other cases, they simply err on the side of caution with unknown substances until more information is available.
When parents have a child with developmental abnormalities, they are often asked to discuss the history of the pregnancy in detail, with a special focus on anything the mother was exposed to, from unusual foods to travel history. While this can be understandably painful, it can provide important information about the potential dangers of poorly studied substances, and being willing to provide detailed information may help other parents avoid such situations in the future.
