Teratology facts for kids

Teratology is the study of how living things develop differently from what is normal. This includes plants and animals throughout their lives. It's a part of medical genetics that looks at how birth defects are classified. A related term, developmental toxicity, covers all kinds of unusual development caused by things in the environment. These can include slow growth, delayed mental development, or other problems without clear physical changes.

Teratogens are substances that can cause birth defects. They do this by having a harmful effect on a baby developing inside its mother (an embryo or fetus). Some known teratogens are retinol, thalidomide, mercury, alcohol, lead, and certain chemicals like polychlorinated biphenyls (PCBs).

What Does "Teratology" Mean?

The word "teratology" comes from two old Greek words. "Teras" meant "monster" or "a sign from the gods." The second part, "-ology," means "the study of."

Long ago, in the 1600s, "teratology" referred to stories about strange or unusual things. By the 1800s, it started to mean the study of unusual biological forms, especially in plants. Today, it mostly means the medical study of birth defects and how they happen.

In the 1960s, a scientist named David Weyhe Smith helped make the term "teratology" well-known. He was one of the researchers who discovered fetal alcohol syndrome. As we learn more about how birth defects happen, teratology now connects with other science fields like developmental biology (how living things grow), embryology (the study of embryos), and genetics (the study of genes).

Before the 1940s, many scientists thought birth defects were mostly passed down through families. But in 1941, the first clear cases showed that things in the environment could also cause severe birth defects.

How Birth Defects Happen in Mammals

Understanding Teratogenesis

As scientists learned that a developing baby inside its mother is very sensitive, they created important guidelines. These are called The Six Principles of Teratology, developed by James G. Wilson in 1959. These rules help us understand how teratogens affect developing living things:

• Rule 1: Genes Matter. How likely a baby is to be affected by a teratogen depends on its genotype (its genetic makeup). It also depends on how these genes react with harmful things in the environment.
• Rule 2: Timing is Key. A baby is more or less likely to be affected depending on its stage of development when it is exposed to something harmful. There are specific times when certain body parts or systems are most sensitive.
• Rule 3: Specific Actions. Teratogens act in particular ways on developing cells and tissues. This starts a chain of events that leads to unusual development.
• Rule 4: Getting to the Baby. How a harmful substance reaches the developing baby depends on many things. These include what the substance is, how much the mother is exposed to, how it crosses the placenta, and the genetic makeup of both the mother and the baby.
• Rule 5: Different Outcomes. There are four main ways that development can go wrong: the baby might not survive, it might have a physical malformation, its growth might be slowed, or it might have problems with how its body works.
• Rule 6: Dose Matters. The more a baby is exposed to a teratogen, the more likely and severe the problems will be. This ranges from no noticeable effect to causing death.

Scientists use animal models like rats, mice, rabbits, and monkeys to test if environmental substances can cause birth defects. Early studies looked for clear physical problems. Today, scientists also study how these substances work at a tiny, molecular level. For example, they use genetically modified mice to see how teratogens affect the development of certain cells, like those that form the Neural crest (which can lead to problems called Neurocristopathies).

Also, there are large studies called pregnancy registries. These studies track what pregnant women are exposed to and the outcomes of their births. This helps provide information about possible risks of medicines or other exposures during human pregnancies. For example, alcohol exposure before birth can cause facial changes, which are seen in Fetal Alcohol Syndrome.

Understanding how a teratogen causes its effects is important. It helps prevent birth defects and can also lead to new, safe medicines for pregnant women.

Alcohol and Pregnancy

Alcohol is known to be a teratogen. Exposure to alcohol before birth is a main cause of birth defects and brain development problems in some parts of the world.

Birth Defects in Humans

In humans, congenital disorders (birth defects) caused about 510,000 deaths worldwide in 2010. About 3% of newborns have a "major physical anomaly." This means a physical difference that affects how they look or how their body works.

Vaccinations During Pregnancy

Vaccinations are very important for preventing diseases like polio, rubella, and COVID-19. Studies have shown that there is no link between birth defects and vaccinations. For example, in Finland, pregnant mothers who received the oral polio vaccine had babies with no difference in outcomes compared to mothers who did not get the vaccine. However, it is still usually not recommended to get the polio vaccine during pregnancy unless there is a risk of infection.

Another important example is the flu vaccine during pregnancy. During the flu outbreaks in 1918 and 1957, many pregnant women died. Even with vaccines available, not many pregnant women get the flu shot. However, studies have shown that there are no harmful effects on the new babies or mothers when the flu vaccine is given during pregnancy.

What Causes Teratogenesis?

Causes of birth defects can be grouped into several types:

• Harmful Substances: These include toxins in the environment during pregnancy.
  • Potassium iodide is a possible teratogen. In its raw form, it can be irritating. Too much exposure over time can affect the thyroid gland.
• Infections: Some infections can pass from the mother to the baby during pregnancy.
• Lack of Nutrients: Not getting enough important nutrients can cause problems. For example, not enough folate acid in a pregnant woman's diet can lead to spina bifida in the baby. Folic acid is a man-made form of folate, often added to foods like flour.
• Physical Pressure: Sometimes, a baby might be physically squeezed inside the womb. An example is Potter syndrome, which can happen if there isn't enough amniotic fluid around the baby.
• Genetic Problems: These are problems with the baby's genes.
• Alcohol Use: Drinking alcohol during pregnancy can cause birth defects.

Teratology in Other Animals

Looking at Old Bones (Fossil Record)

Scientists who study ancient diseases and injuries, called paleopathologists, look for signs of birth defects in fossils. Fossils with these signs are important because they help scientists understand how life's development has changed over time. For example, a Tyrannosaurus rex fossil was found with a block vertebra (a fused backbone). This suggests that backbones have developed in a similar basic way since the time of dinosaurs and mammals.

Other interesting fossil deformities include a baby Troodon (a bird-like dinosaur) with a twisted jaw. Another notable fossil was a Hyphalosaurus (an ancient reptile) that had two heads. This is the oldest known example of having two heads, a condition called polycephaly.

Teratology in Plants

In botany (the study of plants), teratology looks at what abnormal plants can teach us. For example, finding unusual flowers—like those with leaves instead of petals—helped prove the "foliar theory." This theory says that all parts of a flower are actually highly specialized leaves.

Types of Plant Deformations

Plants can have changes that lead to different kinds of unusual shapes:

• Fasciation: The growing tip of the plant becomes flat instead of round.
• Variegation: Parts of the plant, like leaves, have unusual color patterns.
• Virescence: Parts of the plant that should not be green, like flowers, turn green.
• Phyllody: Flower parts or fruits change into leaves.
• Witch's broom: Many branches grow unusually close together at the top of a plant, especially a tree.
• Pelorism: A flower that normally has a mirror-like symmetry (like a snapdragon) changes back to a more radial symmetry (like a daisy).
• Proliferation: An entire organ, like a flower, grows repeatedly.

It's important to know that Galls are not part of plant teratology. Galls are growths caused by outside factors, like insect bites or parasites, not by the plant's own development going wrong.

See also

In Spanish: Teratología para niños