What Causes Birth Defects? Part 3

Common Birth Defects

There are more than 4,000 types of known birth defects. They’re typically classified as structural or functional/developmental. Structural defects are when a specific body part is missing or malformed. The most common structural defects are:

• heart defects
• cleft lip or palate (when there’s an opening or split in the lip or roof of the mouth)
• spina bifida (when the spinal cord doesn’t develop properly)
• clubfoot (when the foot points inward instead of forward)

Functional or developmental birth defects cause a body part or system to not work properly. These often cause disabilities of intelligence or development. Functional or developmental birth defects include metabolic defects, sensory problems, and nervous system problems. Metabolic defects cause problems with the baby’s body chemistry.

The most common types of functional or developmental birth defects include:

• Down syndrome (causes delay in physical and mental development)
• sickle cell disease (when the red blood cells become misshapen)
• cystic fibrosis (damages the lungs and digestive system)

Some children experience physical problems associated with specific birth defects. However, many children show no visible abnormalities. Defects can sometimes go undetected for months or even years after the child is born. 

                                                      Written by The Healthline Editorial Team
                          Medically Reviewed by Laura E. Marusinec, M.D. on December 15, 2015