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Q:
What
is a birth defect?
A birth defect is a problem that
happens while the baby is developing in the mother’s body.
Most
birth defects happen during the first 3 months of pregnancy.
A birth
defect may affect how the body looks, works, or both.
It can be found before birth, at birth, or anytime after birth.
Most defects are found within the first year of life.
Some birth defects (such as cleft lip or clubfoot) are easy to see,
but others (such as heart defects or hearing loss) are found using special
tests (such as x-rays, CAT scans, or hearing tests).
Birth defects can vary from mild to severe.
Some birth defects can cause the
baby to die. Babies
with birth defects may need surgery or other medical treatments, but, if
they receive the help they need, these babies often lead full lives.
[Return to Questions]
Q: What are the most common birth
defects?
One of
every 33 babies is born with a birth defect. A birth defect can affect
almost any part of the body. The
well being of the child depends mostly on which organ or body part is
involved and how much it is affected.
Many birth
defects affect the heart. About 1 in every 100 to 200 babies is born with a
heart defect. Heart defects make up about one-third to one-fourth of all
birth defects. Some of these heart defects can be serious, and a few are
very severe. In some places of the world, heart defects cause half of
all
deaths from birth defects in children less than 1 year of age.
 Other
common birth defects are “neural tube defects,” which are defects of
the spine (spina
bifida) and brain (anencephaly).
They
affect about 1
of 1,000 pregnancies. These defects can be serious and are often life
threatening. They happen less often than heart defects, but they cause many
fetal and infant deaths.
Birth
defects of the lip and roof of the mouth are also common. These birth
defects, known as “orofacial clefts,” include cleft lip, cleft palate,
and combined cleft lip and cleft palate.
Cleft lip is more common than
cleft palate.
 In many places of the world, orofacial clefts affect about 1
in 700 to 1,000 babies.
Some birth
defects are common but rarely life threatening, though they often require
medical and surgical attention. “Hypospadias,” for example, is a fairly
common defect found in male babies. In babies with hypospadias, the opening
of the urethra (where urine comes out) is not at the tip of the penis but
on the underside. Treatment depends on how far away from the tip the
opening is and can involve complex surgery. This defect is rarely as
serious as the others listed above, but it can cause great concern and
sometimes has high medical costs. It
rarely causes death.
These
are only some of the most common birth defects. Two final points are worth
noting. First, genetic conditions, though not mentioned so far, also occur
often. Down syndrome, for example, is a genetic condition that affects
about 1 in 800 babies, but it affects many more babies who are born to
older women. Second, a woman who is pregnant may miscarry a baby (fetus)
early, before it is time for the baby to be born.
This often happens when the fetus has a severe birth defect.
To know the true impact of birth defects and how often they occur,
we not only need to look at babies born but also, if possible, look at all
pregnancies.
[Return to Questions]
Q: What
is my chance of having a baby with a birth defect?
In the United States, about 3% of
babies are born with birth defects. Some
women have a higher chance of having a child with a birth defect.
Women over the age of 35 years have a higher chance of having a
child with Down syndrome than women who are
younger. If taken when a woman is pregnant, certain drugs can
increase the chance of birth defects.
Also, women who smoke and use alcohol while pregnant have a higher
risk of having a baby with certain birth defects.
Other women have a higher chance of having a baby with a birth
defect because someone in their family had a similar birth defect. To learn
more about your risk of having a baby with a birth defect, you can talk
with a genetic counselor.
(To find a genetic counselor, see Where can
I find a geneticist or genetic counselor?) Also,
to reduce your chances of having a baby with a birth defect, talk with your
health care provider about any medicines that you take, do not drink
alcohol or smoke, and be sure to take 400 micrograms of the B vitamin folic
acid every day. It is the
amount of folic acid found in most multivitamins.
[Return to Questions]
Q: Do genetic factors play a
role in causing birth defects?
Yes, in some but not all cases. Changes in the genes can cause certain
birth defects in infants. Genes tell each cell in the body how to
combine with other cells to form parts of the body. For example, genes
tell certain cells to make the heart, the kidneys, or the brain, and
they tell other cells to make our physical features, like green eyes or
brown hair. Genes also tell the cells how to work in the body. Genes
give instructions for cells in our heart to beat, our stomach to digest
food, our muscles to push and pull, and our brain to think.
Genes combine with many other genes to make chromosomes. Changes in
single genes, groups of genes, or entire chromosomes can sometimes cause
birth defects. These genetic changes might happen only in the infant, or
they might pass down from one or both parents. Sometimes, there are
other relatives in the family with the same birth defect, but not
always.
Factors other than genetics can also increase the chance of having a
baby with a birth defect. (See
Does alcohol cause birth defects?
Does
smoking cause birth defects?
Do
illegal drugs cause birth defects?).
In some cases, the mother or baby has genes that are easily affected by
factors outside the body that cause birth defects. In this case, genes
and environment work together to cause a birth defect.
[Return to
Questions]
Date:
July 18, 2007
Content source: National Center on Birth Defects and Developmental
Disabilities
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