There are two main categories of birth defects.
Structural Birth Defects
Structural birth defects are related to a problem with body parts and structure. 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
Functional, or Developmental Birth Defects
Functional, or developmental, birth defects are related to a problem with how a body part or body system works. These problems often lead to intellectual and developmental disability (IDD) and can include:
- Nervous system or brain problems. These include IDDs, behavioral disorders, speech or language difficulties, seizures, and movement trouble. Some examples of birth defects that affect the nervous system include Down syndrome, Prader-Willi syndrome, and Fragile X syndrome.
- Sensory problems. Examples include hearing loss and visual problems, 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 phenylketonuria (pronounced fee-nill-key-toe-NURR-ee-uh) and hypothyroidism (hahy-puh-THAHY-roi-diz-uhm).
- 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 dystrophy and X-linked adrenoleukodystrophy (pronounced uh-DREE-noh-loo-koh-DIS-truh-fee), which leads to problems of the nervous system and the adrenal glands and was the subject of the movie "Lorenzo’s Oil."
In some cases, birth defects are caused by a combination of factors. Some recognized patterns of birth defects affect many parts or processes in the body, leading to both structural and functional problems.