What is Teratogenicity?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 15 July 2018
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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.


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Post 3

This seems like a very scary thing. Who knows what kinds of things could actually be terartogenic agents and we have no idea! People are always inventing new stuff -- new chemicals, new medicines, new everything.

And sometimes it's too late when we find out how harmful it is. It's kind of like cigarettes. Once upon a time, people thought they were harmless!

Post 2

Is this why pregnant women are not supposed to handle kitty litter? Does kitty litter have teratogenicity in pregnancy?

I never understood why women were told this before. I have been pregnant four times, and always made sure to avoid the kitty litter, but it seemed kind of silly. Plus, I thought it had to do with what the cats left in the litter, but maybe it's what the kitty litter itself is made from?

Silly or not though, it was a good excuse to not have to empty the litter box!

Post 1

Does this pertain only to substances that a pregnant woman may be exposed to, or can an illness be a teratogenic agent? I know that I have heard many times that people with certain illnesses, which are normally harmless and go away by themselves, are told to stay away from pregnant women because the illness could harm an unborn child.

I actually had one of these experiences. I was pretty sick, but it just seemed like a bad cold. When I went to the doctor though, they said it could be something called Fifths Disease. They said I would be fine and that it would go away just like a cold would, but that I needed to stay away from pregnant women. The doctor said that if a pregnant women were to get the disease, she would be fine but that the unborn baby might not.

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