BIRTH DEFECTS

BIRTH DEFECTS

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.

Genetic

Genetic defects can be caused by errors in one or more genes passed on by the parents (inherited defects), by a missing, damaged, or extra chromosome (chromosomal disorders), or by a mixture of factors (multifactorial defects).

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.

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