New Jersey Environmental Public Health Tracking Program

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Birth Defects and Human Health

What are Birth Defects?

Birth defects are defined as abnormalities of structure, function, or body metabolism that are present at birth. These abnormalities can lead to mental or physical disabilities, or if very severe can be fatal. There are more than 4,000 different known birth defects that can be present in a newborn.  The American College of Obstetricians and Gynecologists has stated that 3 out of every 100 babies born in the United States has some type of birth defect.  Genetics and environmental factors are thought to play a key role in some defects, although many defects also arise from unknown causes.  In addition, birth defects can develop from a combination of factors.

How Do Birth Defects Affect Human Health?

Birth defects generally are grouped into three major categories: structural or metabolic; congenital infections; and other conditions. 

When a baby has a structural birth defect, some part of the body is either missing or malformed. Heart defects are the most common type of structural birth defect, affecting one baby in 125. While advances in surgery have dramatically improved the outlook for affected babies, these defects remain the leading cause of birth defect-related infant deaths.  Many structural defects can be corrected with surgical intervention, which can then allow the baby to continue to develop normally. 

Metabolic defects affect one in 3,500 newborns. These disorders may not be initially detected at the time of birth, but can lead to adverse physical effects, mental retardation or death.  Many of these conditions result from an inability of cells to produce an enzyme (protein) needed to change certain chemicals into others, or to carry substances from one place to another within the body. 

Congenital infections, such as rubella or sexually transmitted infections, can cause deafness, heart defects, mental retardation, other disorders or can even result in death when passed to the developing fetus.  Other conditions, such as drug use during pregnancy, can cause a wide array of adverse health effects throughout the life of a child, including learning disorders, neurologic disorders, and delayed development.

What is Being Done to Prevent Birth Defects?

Research is being conducted to determine how environmental exposures of the mother during specific periods of fetal development may lead to birth defects.  It is known that alcohol consumption during pregnancy, smoking cigarettes, drug use, certain chemical exposures, as well as metabolic imbalances and other exposure conditions can adversely affect a developing fetus.  However, much more research is still needed to more fully understand how and when these exposures are related to birth defects. 

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