What are Birth Defects? - Causes, Types & Prevention

Instructor: Dana Dance-Schissel

Dana teaches social sciences at the college level and English and psychology at the high school level. She has master's degrees in applied, clinical and community psychology.

Birth defects are abnormalities caused by genetics or exposure to harmful substances in the womb. This lesson discusses causes and types of birth defects as well as their prevention. It wraps up with a quiz to test your knowledge.

Causes and Types of Birth Defects

When you think of a newborn, you probably imagine a chunky, beaming baby with ten fingers and ten toes. Unfortunately, not all babies are so perfect. Approximately 8 million babies around the world are born with birth defects each year. Sometimes, these defects are visible, such as a cleft palate, while other times they're not, as with hearing problems.

Birth defects can be genetic or environmental in nature. Keep reading to learn about differences between the two.

This baby has a cleft palate, a birth defect that is visible at birth.
cleft palate

Genetic Birth Defects

Genetic birth defects occur more often than those of environmental origins. These types of problems are present prior to conception, in the reproductive material of one or both parents. With genetic birth defects, the genetic material that is inherited by the baby from the parents is flawed. Most often, a genetic mutation or chromosomal abnormality causes the defect.

Down syndrome, sickle cell anemia, muscular dystrophy, club foot and even some psychological disorders are examples of genetic birth defects. However, not all children who inherit flawed genes from one or both parents will develop birth defects.

Environmental Birth Defects

Environmental birth defects occur after conception and are much less common than genetic birth defects. One cause of environmental birth defects is prenatal exposure to harmful substances while in the womb. These toxic substances are called teratogens and include things like drugs, alcohol, medications, vaccines, radiation, stress and illness. Inadequate consumption of vital nutrients and minerals during pregnancy is another potential cause of environmental birth defects. Fetal alcohol syndrome, microcephaly, limb deformities and discoloration of the teeth are examples of environmental birth defects.

Not all babies who are exposed to teratogens in the womb develop birth defects. Length of exposure, toxicity of the teratogen and timing of the exposure can impact whether the developing child will be affected. For example, weeks two through seven of embryonic development are prime periods for the development of the heart. So if the embryo is exposed to a teratogen during this period, it's more likely that the development of the heart will be affected.

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