What Are Birth Defects?
While still in the womb, some babies have problems with how their organs and body
parts form, how they work, or how their bodies turn food into energy. These health
problems are called birth defects.
There are more than 4,000 different kinds of birth defects, ranging from minor
ones that need no treatment to serious ones that cause disabilities or require medical
or surgical treatment.
What Are the Types of Birth Defects?
If a baby is born with a part of the body that is missing or malformed, it is called
a structural birth defect. Heart defects
are the most common type of structural defect. Others include spina
bifida, cleft palate, clubfoot,
and congenital dislocated hip.
When there is a problem with a baby's body chemistry, it is called a metabolic
birth defect. Metabolic defects prevent the body from properly breaking down
food to create energy. Examples of metabolic defects include Tay-Sachs
disease, a fatal disease that affects the central nervous system, and phenylketonuria
(PKU), which affects the way the body processes protein.
For people who want to become parents, it's important to know that some birth defects
can be prevented. During a woman's pregnancy, taking folic
acid and getting enough iodine in the diet
can help prevent some types of birth defects. But it's also important to realize that
most babies born with birth defects are born to two healthy parents with no obvious
health problems or risk factors.
What Causes Birth Defects?
In most cases, doctors don't know what caused a baby's birth defect. When the cause
is known, it might be environmental (such as a baby's exposure to chemicals or viruses
while in the womb), a problem with genes, or a combination of these things.
Environmental Causes
If a mother has certain infections (such as toxoplasmosis)
during pregnancy, her baby can have a birth defect. Other conditions that cause defects
include rubella and chickenpox
(varicella). Fortunately, many people get vaccinated against these diseases so these
infections are rare.
Also, alcohol abuse by the mother may cause fetal
alcohol syndrome, and certain medicines taken by the mother can cause birth defects.
(Doctors try to avoid harmful medicines during pregnancy, so a pregnant woman should
tell any doctor she consults that she's expecting.)
Genetic Causes
Every cell in the body has chromosomes containing genes that determine a person's
unique characteristics. During conception, a child inherits one of each pair of chromosomes
(and one of each pair of the genes they contain) from each parent. An error during
this process can cause a baby to be born with too few or too many chromosomes, or
with a damaged chromosome.
One well-known birth defect caused by a chromosome problem is Down
syndrome. A baby develops Down syndrome after getting one extra chromosome. Other
genetic defects happen when both parents pass along a faulty gene for the same disease.
A disease or defect also can happen when only one parent passes along the gene
for that disease. This includes birth defects such as achondroplasia (a form of dwarfism) and Marfan
syndrome.
Finally, some boys inherit disorders from genes passed onto them only by their
mothers. These defects, which include conditions like hemophilia
and color blindness, are called X-linked because the genes are carried on the X chromosome.