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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.
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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.
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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.
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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.
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Questions]
Date:
March 11, 2009
Content source: National Center on Birth Defects and Developmental
Disabilities
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