Some defects can be detected before birth, and some can be prevented. Sometimes a birth defect can be treated with medication, surgery, or diet. This pamphlet will explain:

Types of birth defects What can be done to prevent defects Risk factors Testing and diagnosis

Birth defects can be mild or serious. Many can be treated.

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 3 months of pregnancy. They can vary from mild to severe.

A birth defect may affect how the body looks, works, or both. It is a problem that results from an error in the way the heart, brain, spinal cord, kidney, bone, muscle, skin, or other body organ developed. Some birth defects can cause the baby to die. Babies with birth defects may need surgery or other medical treatments. If they get the treatment they need, they often can lead full lives.

A birth defect can be found before birth, at birth, or any time after birth. Some defects are easy to see right away. Special tests may be needed to find others, such as heart defects or hearing loss. Some problems do not appear until later in a person's life.

About one out of every 33 babies born each year in the United States has a birth defect. For about 70% of babies born with birth defects, the cause is not known. With some birth defects, there are no known risk factors.

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. Some of these types overlap.

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. Some of these heart problems are mild. Others are so severe they result in death.

Neural tube defects are another common structural birth defect. These are defects that result when the coverings over the spinal cord or brain do not close properly. Neural tube defects include spina bifida and anencephaly.

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.

Chromosomal disorders are most often the result of an error that occurred when the egg and sperm were joining. The older you are, the greater your risk of having a child with a chromosomal disorder. The most common chromosomal disorder is Down syndrome.

Multifactorial defects can result from the interaction of the parents' genes with the environment of the developing fetus. The causes of these disorders are not clear. Abdominal wall defects, cleft palate, and clubfoot can be examples of multifactorial defects.

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. Another way these defects can occur is if the mother is exposed to high amounts of toxic agents such as mercury, lead, or radiation during pregnancy.

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. If you are thinking about getting pregnant, visit your doctor first.

A pre-pregnancy visit is especially important for women who have medical problems, such as diabetes or epilepsy. Birth defects are more common in babies whose mothers have these conditions. Ask your doctor what changes, if any, need to be made to bring your condition under control before you try to get pregnant.

Folic Acid

Taking supplements or eating foods with folic acid can help prevent neural tube defects. To do this, they must be taken before you get pregnant and in early pregnancy. The time when the developing neural tube needs the folic acid often occurs before a woman knows she is pregnant. Therefore, all women of childbearing age should take a daily multi-vitamin containing 0.4 mg of folic acid.

If you have had a child with a neural tube defect, you are more likely to have another child with this problem. You need an extra-high daily dose of folic acid—10 times the normal preventive amount. Ask your doctor for a prescription for this amount. You should not take it as several multivitamins because high doses of the other vitamins in the pill may be harmful.

Alcohol and Other Drugs

Alcohol use during pregnancy is a leading cause of mental retardation. Some babies exposed to large amounts of alcohol during pregnancy develop fetal alcohol syndrome. Babies with fetal alcohol syndrome may have many problems, including mental retardation, heart defects, and defects of their joints and limbs.

It is not clear how much, if any, alcohol is safe to drink during pregnancy. For this reason, pregnant women should avoid drinking any alcohol.

Some illegal drugs can cause slow fetal growth and learning problems. Other drugs have not been studied enough to know how their use affects specific birth defects.

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. The risk of the fetus getting infected is greatest if a woman gets infected for the first time when she is pregnant. A lab test can be done to find out if a woman has already been infected with CMV. Pregnant women often acquire CMV from young children. The best way to prevent infection from CMV is to wash your hands often, especially after contact with a child who is in day care.

Rubella (German measles) can cause deafness, mental retardation, heart defects, and blindness. If you have not already had the disease or been vaccinated, you should be vaccinated against rubella at least 1 month before becoming pregnant.

Sexually transmitted diseases (STDs) can cause serious birth defects. For instance, syphilis or herpes infection can cause severe problems, including blindness and death. You will be tested for some STDs at your first prenatal visit. Treating an STD may prevent or reduce damage to the fetus.

Other Factors Affecting Birth Defects

Exposure to toxic agents such as lead or mercury can cause birth defects. If you think you may be exposed to a harmful agent at work, talk to your employer about it.

Pregnant women should not eat certain fish that have high mercury levels. The fish to avoid are shark, swordfish, king mackerel, or tilefish. Other types of fish should be limited to 12 ounces per week, and albacore tuna and tuna steaks should be limited to 6 ounces per week.

Radiation in high doses, such as that used to treat cancer, can harm a fetus. The smaller doses used for most tests are not harmful in most cases.

Very high levels of vitamin A have been linked with severe birth defects. Your prenatal multivitamin should contain no more than 5,000 international units (IUs) of vitamin A. Some supplements have up to 25,000 IUs of vitamin A in each dose.

Certain medications can cause defects. Tell anyone who prescribes drugs for you that you are pregnant. That includes any doctors you see for non-pregnancy problems, mental health providers, and your dentist. Don’t stop taking a medicine prescribed for you without talking to your doctor. Also, check with your doctor before taking any over-the-counter drugs. This includes pain relievers, laxatives, cold or allergy remedies, vitamins, herbal products, and skin treatments.

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

Risk Factors for Genetic Disorders If the answer to any of these questions is yes, you may be at increased risk for having a baby with a genetic disorder. Will you be 35 years or older when your baby is due? Will the baby's father be 50 years or older when your baby is due? If you or your partner are of Mediterranean or Asian descent, do either of you or anyone in your families have thalassemia (an inherited disorder that causes anemia)? Is there a family history of neural tube defects? Have you or the baby's father ever had a child with a neural tube defect? Is there a family history of congenital heart defects? Is there a family history of Down syndrome? Have you or the baby's father ever had a child with Down syndrome? If you or the baby's father are of eastern European Jewish, French Canadian, or Cajun descent, is there a family history of Tay–Sachs disease? If you or the baby's father are of eastern European Jewish descent, is there a family history of Canavan disease? If you or the baby's father are African American, is there a family history of sickle cell anemia or sickle cell trait? Is there a family history of hemophilia? Is there a family history of muscular dystrophy? Is there a family history of cystic fibrosis? Is there a family history of Huntington's disease? Does anyone in your family or the family of the baby's father have cystic fibrosis? Is anyone in your or the baby's father's family mentally retarded? If so, was that person tested for fragile X syndrome? Do you, the baby's father, anyone in your families, or any of your children have any other genetic diseases, chromosomal disorders, or birth defects? Do you have a metabolic disorder such as type 1 or type 2 diabetes or phenylketonuria? Do you have a history of pregnancy issues (miscarriages or a stillborn baby)?

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. It will not tell you if your baby has a defect. There are several types of screening tests: carrier screening, ultrasound, and maternal serum screening. A positive screening test result suggests that you may want to have further diagnostic tests to check your baby's health.

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 do not look for all birth defects that could occur.

Tests also are not 100% accurate. Your fetus could have a birth defect even if testing does not show a problem. Also, a test result could be positive even though your baby is healthy. A genetic counselor can explain what the test results mean. He or she also can tell you how accurate the result is.

Carrier Screening

Some birth defects are inherited. Just as a baby gets certain traits like eye color from the parents, certain diseases or disorders can be passed on to the baby. Carrier screening is done to see if a couple carries a defective gene for certain inherited disorders. For this test, a sample of a person's blood or saliva is studied in a lab. A carrier screening test can be done before pregnancy, during pregnancy, or after pregnancy.

Carrier screening can be done to check for a number of genetic disorders. These include cystic fibrosis, sickle cell anemia, Tay–Sachs disease, Canavan disease, fragile X syndrome, Duchenne muscular dystrophy, hemophilia, and Huntington's disease.

It is up to you to decide if you wish to be tested. If the test shows you are a carrier, the next step is to test the baby's father. If the test shows that both parents are carriers, a genetic counselor can give you more information about the risk of having a baby with the disorder. Further testing may be available to show if the fetus has the defect.

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. If you already have an increased risk of having a baby with one of these problems, you may be offered a diagnostic test instead.

With maternal serum (blood) screening, several tests often are performed together. This is known as "multiple marker screening." These tests measure the level of three or four of the following substances in your blood: estriol, human chorionic gonadotropin, alpha-fetoprotein, and inhibin-A. These are all substances produced by the fetus or the placenta during pregnancy. Maternal serum screening is done at 15–20 weeks of pregnancy.

If one or more of the test results are not in the normal range, your doctor will offer you further testing. In almost all cases, a follow-up test shows that the baby is fine.

First Trimester Screening

This screening test is done between 10 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. Diagnostic tests include a detailed ultrasound exam, chorionic villus sampling, amniocentesis, and cordocentesis. If any of these tests show that your baby will have a birth defect, you will receive counseling about what this will mean for your family.

Detailed Ultrasound Exam

A comprehensive or detailed ultrasound exam looks for specific problems in the fetus. It is done if you have a family history showing risks for birth defects, if there is an abnormal result in the maternal serum screening tests, or if an ultrasound screening exam shows a possible problem.

If heart problems are suspected, a fetal echocardiogram (a special ultrasound exam of the heart) also may be done. This kind of study examines the baby's heart more thoroughly than an exam done with standard ultrasound.

Chorionic Villus Sampling

Chorionic villus sampling is used to find chromosomal problems in the fetus, including Down syndrome and trisomy 18. It studies a small sample of tissue from the placenta. Chorionic villi (the plural of villus) in the placenta have the same genetic makeup as the fetus. This test can be performed early in pregnancy—often at 10–12 weeks.

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. Also, testing the AFP level in the amniotic fluid can help determine if the fetus has a neural tube defect. Sometimes amniocentesis will show that your baby does not have a birth defect even though previously there was an abnormal screening test result.

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. Cordocentesis usually is used when a diagnosis cannot be made with ultrasound, chorionic villus sampling, or amniocentesis.

The Next Steps

If diagnostic tests show that your baby will have a birth defect, your doctor will talk to you about your options. In many cases, it is not known how severe a birth defect will be. Sometimes prenatal surgery or treatment can be done. In most cases, there is no prenatal treatment for a defect.

You may have to make some hard choices in a short time. Talk about the facts and your feelings with your partner, your doctor, and others with whom you can share your thoughts. There is no "right choice." Your next steps depend on your baby's outlook, options for treatment, your values, your finances, and your support system.

Some couples choose to terminate the pregnancy when a major problem is found. If this is your choice, it can be hard to come to terms with your loss and move on. The support of your loved ones is vital. Allow yourself time to grieve. You may want to seek counseling.

Other couples choose to continue the pregnancy even if the baby will have a problem. A baby with major health problems can be a valued part of your family and your life. With help from your doctor and your loved ones, you can start to plan for your child's future. If this is your choice, use the months before the birth to prepare yourself and your family. Line up special care from medical experts. Arrange to give birth at a hospital with facilities and specialists to care for your baby. Read as much as you can about your baby's condition. Join support groups for parents of children with the condition.

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.

Glossary

Abdominal Wall Defects: Birth defects in which the muscle and skin that cover the wall of the abdomen are missing and the bowel is either contained within a clear walled sac (omphalocele) or sticks out through a hole in the abdominal wall (gastroschisis).

Amniotic Fluid: Water in the sac surrounding the fetus in the mother's uterus.

Anencephaly: A type of neural tube defect that occurs when the fetus's head and brain do not develop normally.

Canavan Disease: A rare inherited disorder that causes the brain to degenerate, with death usually occurring before age 4 years. It is more frequent in people of eastern European Jewish descent (Ashkenazi Jews).

Carrier: A person who shows no signs of a particular disorder but could pass the gene on to his or her children.

Chromosome: A structure that is located inside each cell in the body and contains the genes that determine a person's physical makeup.

Cleft palate: A birth defect in which a gap or space occurs in the roof of the mouth.

Clubfoot: A birth defect in which the foot is misshaped and twisted out of position.

Cystic Fibrosis: An inherited disorder that causes problems in digestion and breathing.

Down Syndrome: A genetic disorder in which mental retardation, abnormal features of the face, and medical problems such as heart defects occur.

Duchenne Muscular Dystrophy: An inherited, sex-linked disease most often affecting males. Symptoms are weakness and muscle wasting, first of the limbs and trunk, but slowly affecting all voluntary muscles, with death usually occurring around age 30 years.

Fetus: A baby growing in the woman's uterus.

Fragile X Syndrome: A disorder of the X chromosome that is the most common inherited cause of mental retardation.

Genes: DNA "blueprints" that code for specific traits, such as hair and eye color.

Hemophilia: An inherited sex-linked disorder in which the blood lacks a substance that helps it clot.

Huntington's Disease: An inherited nerve disorder that causes loss of control of movements and mental function, usually starting between 35–50 years of age.

Nuchal Translucency Screening: A special ultrasound test of the fetus to screen for the risk of Down syndrome and other birth defects.

Placenta: Tissue that provides nourishment to and takes away waste from the fetus.

Sickle Cell Disease: An inherited disorder in which red blood cells have a crescent shape, causing chronic anemia and episodes of pain. It occurs most often in African Americans.

Spina Bifida: A neural tube defect that results from incomplete closure of the fetal spine.

Tay–Sachs Disease: An inherited birth defect that causes mental retardation, blindness, seizures, and death, usually by age 5 years. It occurs mostly in people of eastern European Jewish descent (Ashkenazi Jews) and among French Canadians.

Trisomy 18: A genetic disorder that causes serious problems with development. Most infants with trisomy 18 die within the first year of life.

Ultrasound: A test in which sound waves are changed to images to examine internal structures. During pregnancy, it can be used to examine the fetus.

This Patient Education Pamphlet was developed under the direction of the Committee on Patient Education of the American College of Obstetricians and Gynecologists. Designed as an aid to patients, it sets forth current information and opinions on subjects related to women's health. The average readability level of the series, based on the Fry formula, is grade 6–8. The Suitability Assessment of Materials (SAM) instrument rates the pamphlets as "superior." To ensure the information is current and accurate, the pamphlets are reviewed every 18 months. The information in this pamphlet does not dictate an exclusive course of treatment or procedure to be followed and should not be construed as excluding other acceptable methods of practice. Variations taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice may be appropriate.

Copyright © March 2005 by the American College of Obstetricians and Gynecologists. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.

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