Genetic Birth Defects: Risk Factors, Epidemiology, and Testing

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  • 0:01 What Is a Birth Defect?
  • 0:57 Examples of Birth Defects
  • 1:42 Risk Factors & Epidemiology
  • 3:41 Testing for Birth Defects
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will define birth defects, point some major ones out, and discuss the many different kinds of risk factors. Finally, it will outline the major categories of tests available for assessing the risk for or diagnosing genetic birth defects.

What Is a Birth Defect?

Thanks to lemon laws and some great return policies, if you get a car or a product that's defective, you can either give it back, get it exchanged, or get it fixed at no cost to you.

But fixing a genetic birth defect isn't always possible. A birth defect is a problem that occurs during a baby's development inside the mother's womb, and genes are like computer code, but for your body. Genes are transferred and copied from parents to children, like computer code can be from one machine to another.

If some computer code doesn't have the right sequence of 1s and 0s, then something funky will happen on your screen. And if the genes don't have the right makeup then, unfortunately, a birth defect may be the end result.

Because genetic birth defects are far more serious and life altering than defects in consumer products, it's important we cover why they occur and how they can be tested for in this lesson.

Examples of Birth Defects

But before we do that, it's important I paint a picture for you of birth defects. So far, you only know the term itself, but we should also look at some famous examples of defects at least partially attributed to genes.

Such birth defects include:

  • Heart defects, such as septal and ventricular defects, which are like holes in the heart. These can result in a failure of the heart if not taken care of. Imagine having a tire pump with a hole in the hose, you'd get tired of pumping really fast, and that's what happens to the heart in these cases over time. Other birth defects include:
  • Down syndrome
  • Spina bifida
  • Cleft lip or palate
  • And, unfortunately, many more

Risk Factors and Epidemiology

In fact, thousands of different kinds of birth defects are wholly, or at least partially, attributed to genes. But over half of the time, we don't know what causes a birth defect.

About eight million children worldwide, amounting to six percent of all births, are born with dangerous birth defects every year. Many of these kids are disabled for life.

And there are a ton of factors that influence the risk of having a child with one genetic birth defect or another. In general, some defects are more common than others. A hole in the heart, called an atrioventricular septal defect occurs in about one in every 2,100 births, while spina bifida occurs once every 2,800 births.

Additionally, some conditions, like Down syndrome, may be more or less common depending on certain factors. On average, Down syndrome occurs in about one out of every 800 children. With increasing maternal age, especially after age 35, the chances of a child being born with Down syndrome increases. As an example, the likelihood a child is born with Down syndrome in a woman who is 40 is one in 100, but it's one in 12 if she is 50.

Race also plays a role in genetic birth defects. Infants born to African-American women are more likely to have a heart condition, composed of four different defects at once, called tetralogy of fallot when compared to non-Hispanic white mothers. However, children born to African-American mothers have a lower prevalence of other defects, like Down syndrome or cleft palate, when compared to white, non-Hispanic women.

Socioeconomics also plays a crucial role in the epidemiology and risk factors associated with genetic birth defects. Most babies with genetic birth defects are born in low-to-middle income nations.

Testing for Birth Defects

Some birth defects can be tested for before or after a child is born using numerous different means, and we'll focus on some of these methodologies.

A carrier test is a test that looks for a gene a person has for an inherited disorder. It can be performed before or during pregnancy. A carrier is a person who has no signs or symptoms of a genetic disorder but can pass it on to their children. Thus, a carrier test will help inform the parents of the risks involved in having a baby, in terms of the chances of the child having a specific condition based on the genetic makeup of the parents.

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