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Just about every mother-to-be worries about her baby having a problem. However, most babies are born healthy. Out of 100 newborns in the United States, only two or three have a serious defect.
What Is a Birth Defect?
A birth defect is something abnormal that is
present at birth. It also is called a congenital disorder. Most birth defects
happen during the first three months of pregnancy. They can vary from mild to
severe.
Types of Birth Defects
More than 3,000 different birth defects are
known. They can be divided into several types, such as structural, genetic and
those caused by exposure to an infectious disease or a harmful chemical agent.
Structural
With a structural birth defect, some part of the baby's
body is missing or is not formed right. Such a defect can be internal, such as a
heart defect, or external, such as a clubfoot. There is no single cause of
structural defects.
Heart defects are the most common type of birth defect. About one in every 125 babies is born with a heart defect.
Neural tube defects are another common structural birth defect.
Some inherited disorders are more common in certain ethnic groups. These include sickle cell disease, Tay-Sachs disease and cystic fibrosis.
The most common chromosomal disorder is Down syndrome.
Exposure to Infections and Harmful Chemical Agents
Some birth
defects can occur when the fetus is exposed to maternal infections or the mother
drinks alcohol in excess or takes certain medicines.
Preventing Birth Defects
Some birth defects cannot be prevented. But
you can decrease your risk of having a baby with a disorder by taking care of
yourself and avoiding harmful substances.
Folic Acid
Taking supplements or eating foods with folic acid can
help prevent neural tube defects.
Alcohol and Other Drugs
Alcohol use during pregnancy is a leading
cause of mental retardation.
Infections
Cytomegalovirus (CMV) is the most common viral
infection in newborn babies. Most CMV infections cause no significant problems,
but in severe cases they may cause mental retardation, deafness, and loss of
vision.
Other Factors Affecting Birth Defects
Exposure to toxic agents
such as lead or mercury can cause birth defects.
Radiation in high doses, such as that used to treat cancer, can harm a fetus.
Certain medications can cause defects.
Risk Factors
Your doctor can help you learn about your risk factors
for having a baby with a birth defect. You may be at an increased risk of having
a baby with a birth defect if you:
· Are aged 35 years or older when the baby is due
· Have a family or personal history of birth defects
· Have previously had a child with a birth defect
· Used certain medicines around the time you became pregnant
· Had diabetes before pregnancy
Screening Tests
A screening test looks for signs that your baby might
have a genetic defect. The result of a screening test shows only if the risk is
present.
Some tests for birth defects are offered to all pregnant women. Others may be offered if your medical history, family history or physical exam raises a question about your baby's health.
Tests also are not 100 percent accurate. Your fetus could have a birth defect even if testing does not show a problem.
Carrier Screening
Some birth defects are inherited. Carrier
screening is done to see if a couple carries a defective gene for certain
inherited disorders.
Ultrasound Screening
An ultrasound exam can be done at any time
during pregnancy. An ultrasound exam can be used to check on the following:
· Fetal organs and structures
· Age of the fetus
· If you're carrying more than one fetus
· How well the fetus is growing
· Location of the placenta
· Fetal heart rate
Maternal Serum Screening
Maternal serum screening tests are used
to find out if you have a higher-than-normal risk of having a baby with neural
tube defects, abdominal wall defects, Down syndrome or trisomy 18.
With maternal serum (blood) screening, several tests often are performed together. This is known as "multiple marker screening."
First Trimester Screening
This screening test is done between 10
weeks and 14 weeks of pregnancy. It combines the results of a special ultrasound
test called nuchal translucency screening and certain blood tests (PAPP-A and
hCG) to look for signs of Down syndrome, trisomy 18 and heart defects.
Diagnostic Tests
If you have an increased risk of having a baby
with a disorder, you may be offered one or more diagnostic tests.
Detailed Ultrasound Exam
A comprehensive or detailed ultrasound
exam looks for specific problems in the fetus.
Chorionic Villus Sampling
Chorionic villus sampling is used to
find chromosomal problems in the fetus, including Down syndrome and trisomy 18.
Amniocentesis
Amniocentesis usually is done at 15-20 weeks of
pregnancy. Fetal cells from a small sample of amniotic fluid are studied under a
microscope to find chromosomal defects or an inherited disorder.
Fetal Blood Sampling
Fetal blood sampling, also known as
cordocentesis, tests for chromosomal defects and other abnormalities in fetal
blood taken from a vein in the umbilical cord.
Finally . . .
Birth defects can be mild or serious. Many can be
treated. You may be able to prevent some birth defects by taking certain steps
before you get pregnant and during pregnancy. Good prenatal care will help you
stay healthy and may help you detect a birth defect in advance.