What is a birth defect?
The term "defect" refers to abnormal development related to body structure, body function, body metabolism, or an error in body chemistry. Typically a defect is present at birth (congenital), but there may be a recognizable defect during pregnancy (prenatal) or following birth (postnatal).
Birth defects can have many causes including genetic mutations, chromosomal abnormalities, environmental exposures, nutrition, and/or random events in the prenatal period. Many defects are thought to be a combination of these factors. Examples of two major categories of birth defects include structural and metabolic defects.
Structural defects typically involve a body part that is missing or malformed. These types of defects can have both genetic and environmental causes. Examples of structural defects include heart defects, and neural tube defects. Other terms often used for these types of defects include anomalies, malformations, or deformities.
Metabolic defects often involve the inability of cells to produce a protein in the correct amount to regulate the chemistry of the body. High sugar levels in persons with diabetes is an example of a metabolic defect in adults. In infants, phenylketonuria, or PKU is one example of this type of defect. Excess phenylalanine in the body is toxic to the central nervous system. Early detection of PKU can prevent brain damage in affected infants.