Birth Defects

What Are the Types of Birth Defects?

File photo. Credit: AlyeskaOpens in new window Birth defects are common, costly, and critical conditions that affect 1 in every 33 babies born in the United States each year.

Birth defects can vary from mild to severe. The well-being of each child affected with a birth defect depends mostly on which organ or body part is involved and how much it is affected. Depending on the severity of the defect and what body part is affected, the expected lifespan of a person with a birth defect may or may not be affected.

Identifying Birth Defects

A birth defect can be found before birth, at birth, or any time after birth. Most birth defects are found within the first year of life.

Some birth defects (such as cleft lip) are easy to see, but others (such as heart defects or hearing loss) are found using special tests, such as echocardiograms (an ultrasound picture of the heart), x-rays or hearing tests.

Types of Birth Defects

Some birth defects affect many parts or processes in the body, leading to both structural and functional limitations. Thus, there are two main categories of birth defects.

1.   Structural Birth Defects

Structural birth defects are related to a problem with the structure of body parts. These can include:

• Cleft lip or cleft palate
• Heart defects, such as missing or misshaped valves
• Abnormal limbs, such as a clubfoot
• Neural tube defects, such as spina bifida, and problems related to the growth and development of the brain and spinal cord

2.   Functional or Developmental Birth Defects

Functional or developmental birth defects are related to a problem with how a body part or body system works or functions. These problems can include:

• Nervous system or brain-related difficulties. These include intellectual and developmental disabilities, behavioral disorders, speech or language difficulties, seizures, and movement trouble. Some examples of birth defects that affect the nervous system include Down syndromeOpens in new window, Prader-Willi syndrome (PWS)Opens in new window, and fragile X syndromeOpens in new window.
• Sensory difficulties. Examples include hearing loss and visual difficulties, such as blindness or deafness.

• Metabolic disorders. These involve problems with certain chemical reactions in the body, such as conditions that limit the body’s ability to rid itself of waste materials or harmful chemicals. Two common metabolic disorders are phenylketonuriaOpens in new window and hypothyroidismOpens in new window.
• Degenerative disorders. These are conditions that might not be obvious at birth but cause one or more aspects of health to steadily get worse. Examples of degenerative disorders are muscular dystrophyOpens in new window and X-linked adrenoleukodystrophyOpens in new window, which leads to problem of the nervous system and the adrenal glands and was the subject of the movie “Lorenzo’s Oil.”

Causes of Birth Defects

Birth defects can occur during any stage of pregnancy. Most birth defects occur in the first 3 months of pregnancy, when the organs of the baby are forming. This is a very important stage of development. However, some birth defects occur later in pregnancy. During the last six months of pregnancy, the tissues and organs continue to grow and develop.

For some birth defects, like fetal alcohol syndrome, we know the cause. But for most birth defects, we don’t know what causes them. For most birth defects, we think they are caused by a complex mix of factors. These factors include our genes (information inherited from our parents), our behaviors, and things in the environment. But, we don’t fully understand how these factors might work together to cause birth defects.

While we still have more work to do, we have learned a lot about birth defects through past research. For example, some things might increase the chances of having a baby with a birth defect, such as:

• Smoking, drinking alcohol, or taking certain drugs during pregnancy.
• Having certain medical conditions, such as being obese or having uncontrolled diabetes before and during pregnancy.
• Taking certain medications, such as isotretinoin (a drug used to treat severe acne).
• Having someone in your family with a birth defect. To learn more about your risk of having a baby with a birth defect, you can talk with a clinical geneticist or a genetic counselor.
• Having certain infections during pregnancy such as Zika virus and cytomegalovirus.
• Experiencing fever greater than 101oF or having an elevated body temperature due to heat exposure.
• Being an older mother, as the risk of chromosomal abnormalities increases with age.

Having one or more of these risks doesn’t mean you’ll have a pregnancy affected by a birth defect. Also, women can have a baby born with a birth defect even when they don’t have any of these risks. It is important to talk to your doctor about what you can do to lower your risk.

Prevention of Birth Defects

Not all birth defects can be prevented. But, there are things that a woman can do before and during pregnancy to increase her chance of having a healthy baby:

• Be sure to see your health-care provider regularly and start prenatal care as soon as it becomes certain that you are pregnant.
• Get 400 micrograms (mcg) of folic acid every day, starting at least one month before getting pregnant.
• Do not drink alcohol or smoke.
• Talk to a health-care provider about any medications you are taking or thinking about taking. This includes prescription and over-the-counter (OTC) medications and dietary or herbal supplements. Do not stop or start taking any type of medication without first talking to a doctor.
• Know how to prevent infections during pregnancy.
• Be proactive in identifying and treating fever when ill or after getting a vaccine. Treat fevers higher than 101^oF with Tylenol^® (or store brand acetaminophen), and avoid hot tubs, saunas, or other environments that might cause overheating.
• If possible, be sure any medical conditions are under control, before becoming pregnant. Some conditions such as diabeties, can increase the risk for birth defects.