Birth defects

Birth defects are structural (how the body is built) or functional (how the body works) abnormalities present at birth that can cause physical disabilities, intellectual and developmental disabilities, and other health problems. This information focuses on structural birth defects, such as heart, limb, or brain malformations, their causes, their prevention, and their treatments. Functional / developmental abnormalities are more fully addressed in the Intellectual and Developmental Disorders (IDD) information .

Researchers have identified thousands of different birth defects, and some are more disruptive than others. If not detected and treated quickly, some can be fatal or cause lifelong disabilities. Currently, the Centers for Disease Control and Prevention notes that birth defects are the leading cause of death for infants during the first year of life.

Understanding human development throughout the lifespan, including birth defects and related or resulting disabilities, was one of the main reasons NICHD was founded. The institute is at the forefront of research on birth defects, their causes, their prevention and treatments, and their long-term health outcomes.

NICHD is aware that the term "birth defects" has negative overtones and that the term does not reflect the many abilities and talents of those affected by these problems. Communities discuss alternative terms to describe these birth problems. Until consensus is reached, this website uses the term "birth defects" to describe these health problems.

What are the types of birth defects?

There are two main categories of birth defects.

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 malformed valves
Abnormal limbs, such as a club foot
Neural tube defects , such as spina bifida , and problems related to the growth and development of the brain and spinal cord

Functional or developmental birth defects

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

Nervous system or brain problems. These include intellectual and developmental disorders, behavioral disorders, speech or language problems, seizures and movement problems. Some examples of birth defects that affect the nervous system include Down syndrome , Prader-Willi syndrome, and Fragile X syndrome .
Sensory Problems. Examples are hearing loss and visual problems such as blindness or deafness.
Metabolic diseases. These include problems with certain chemical reactions in the body, such as conditions that limit the body's ability to remove waste or harmful chemicals. Two common metabolic disorders are phenylketonuria and hypothyroidism.
Degenerative conditions. These are conditions that may not be obvious at birth, but they cause one or more aspects of health to deteriorate steadily. Examples of degenerative conditions are muscular dystrophy and X-gebound adrenoleukodystrophy, leading to nervous system and adrenal problems and was the subject of the movie "Lorenzo's Oil".

Some birth defects affect many parts or processes in the body, leading to structural as well as functional problems.

This information focuses on structural birth defects, their causes, their prevention and their treatment. Functional / developmental birth defects are more fully addressed in the content of intellectual and developmental disorders .

Different birth defects have different causes, and the causes of many birth defects remain unknown.

A specific condition can be caused by one or more of the following primary problems: ¹

Genetic problems. One or more genes can have a change or mutation that prevents them from working properly, such as in Fragile X syndrome . Likewise, a gene or part of the gene may be missing.
Chromosomal problems. In some cases, a chromosome or part of a chromosome may be missing, such as with Turner syndrome , when a woman is missing an X chromosome. Other birth defects are the result of having an extra chromosome, such as Klinefelter syndrome and Down syndrome .
Infections. Women who get certain infections during pregnancy are at greater risk of having a child with birth defects. For example, infection with the Zika virus during pregnancy is linked to a birth defect called microcephaly, where the brain and skull are smaller than normal.Zika infection in pregnancy is also linked to other structural brain problems . Our Pregnancy topic provides more information about infections that can cause birth defects and other problems in newborns and ways to prevent them during pregnancy , and CDC provides tips for preventing infections before and during pregnancy .
Exposure to drugs, chemicals, or other agents during pregnancy. The infants whose mothers have taken thalidomide are examples of exposure leading to birth defects. Other examples include exposure to rubella (also called German measles) and toxic chemicals, such as hydrocarbons. ²

Birth defects

What are the types of birth defects?

What Causes Birth Defects?