AFP Testing for Improved Pregnancy Outcome
Introduction
Every pregnant woman hopes that her baby will be healthy at birth. It is helpful for your doctor to know as much as possible about the health of your developing baby, (called a fetus), early in pregnancy. Now the AFP (alpha- fetoprotein) screening test can give your doctor more information than ever before. This test is helpful in identifying high risk pregnancies and some types of birth defects.
The AFP test is a blood test which is done when a woman is between 16 and 18 weeks pregnant. You will be asked to give your permission before the test is done. This information has been written to provide you with information about the test so that you can decide whether or not you want to be tested. Read the information carefully. It is a good idea to discuss it with the baby's father, a relative, or a close friend. If anything you read is unclear, ask your doctor. Then, if you want to have the test, you will be asked to sign a consent form.
What is AFP Testing?
AFP (alpha-fetoprotein) is a protein which is made by all unborn babies. AFP can be measured in the mother's blood. When there is too much or too little AFP in the mother's blood, it is a signal to the doctor to check the pregnancy more carefully. The AFP screening test identifies women who may be further along, or not as far along, in their pregnancy as they thought. It can also pick up twins and help to identify women who may be at risk of having a premature delivery or a low birth weight baby. The test can also identify women who are carrying a fetus with a neural tube defect, or other severe birth defects such as a kidney or abdominal wall defect.
What are Neural Tube Defects?
Neural tube defects are quite rare. Out of 1,000 pregnant women, only one or two will have a baby born with a neural tube defect. Neural tube defects are birth defects in which the brain or part of the spinal cord does not form normally, and may not be covered with skin or bone. In the first weeks of pregnancy, when the fetus is less than one inch long, the brain and spinal cord begin to form. They form from a structure along the back of the fetus called the neural tube. The top of the tube develops into the brain; the rest of the tube becomes the spinal cord. Neural tube defects occur when the neural tube does not close properly to form the brain or spinal cord. The exact causes of neural tube defects are unknown, but heredity plays a part.
The two major types of neural tube defects are anencephaly and spina bifida.
Anencephaly occurs when the brain and head do not develop normally. Babies with anencephaly are almost always stillborn or die shortly after birth.
Spina bifida can either be open or closed. Open spina bifida - sometimes called 'open spine' occurs when the lower part of the neural tube is open and the spinal cord and nerves are exposed outside the body. Some babies with open spina bifida die. Those that survive infancy usually have medical problems, some more severe than others.
Most children with open spine also have hydrocephalus (water on the brain). A few are mentally retarded, but most are not. Many children with open spina bifida cannot control their bowels and bladder. These children will also frequently have loss of sensation in the lower part of the body. They often require operations, braces, and physical therapy to walk and to have a chance to lead as normal a life as possible.
In closed spina bifida. The spinal cord is not exposed outside the body, but is covered with skin which has grown over the defect. Closed spina bifida creates the same handicaps, but is usually less severe. Closed spina bifida is usually not detected by AFP testing.
Research continues into the causes and treatment of neural tube defects. It is hoped that in the coming years, advances in medical science will make it possible to prevent these disorders altogether. Meanwhile, AFP testing offers the best available means for early diagnosis of anencephaly and open spina bifida.
What are the GOOD POINTS about having AFP Testing?
The test is simple and safe. The risk of this blood test is no greater than for any other blood test.
It gives the doctor important information. Identifying high risk pregnancies early will alert your doctor to watch your pregnancy more closely. Clearly, it is very important for the doctor to know if the fetus has a severe birth defect. Twins or a change in due date will change the plans for delivery.
Recent studies have shown that low AFP might also be important. Low AFP is associated with a higher risk of miscarriage and with a higher chance of having a baby with a chromosome disorder, such as Down Syndrome.
It gives the parents a choice. AFP testing is done when a woman is about four months pregnant. When a high or low level is found, further tests can be recommended to look for the reason. If a neural tube defect or other severe birth defect is found, the parents may decide to end the pregnancy and try again for a healthy baby.
However, parents who would not consider ending the pregnancy may still want the information about their baby that this test can provide. It may improve the baby's chances. If the parents choose to continue the pregnancy, the baby with a neural tube defect should be born in a hospital with special equipment and treated by doctors who are specially trained. Knowing in advance gives parents time to make arrangements to have the baby born under the best possible circumstances, and to adjust emotionally.
What Are The BAD POINTS About AFP Testing?
The test presents a slight risk to the mother. There may be a little discomfort when the blood is drawn. Also, there is a small chance of a bruise, slight bleeding, infection, or fainting.
The parents may worry over the results. Some parents feel anxious or worry while they wait for the results. However, it is important to remember that most babies do not have neural tube defects or other serious problems.
The AFP blood test is only a screening test. Remember, a positive blood test does not necessarily mean something is wrong. If the blood test is positive. Other tests will be needed to find out if something is really wrong. Less than 5 out of every 100 women whose blood test is positive will be carrying a baby with a neural tube defect.
If the first test is positive, either high or low, another blood sample may be taken and the test repeated. Even then, the doctor may not know for sure and other tests may be recommended. These tests include a sonograrn (sound wave picture) and possibly amniocentesis (drawing fluid from the bag of water). Women who have to have these other tests do feel anxious. However, it is important to remember that almost all women need only one blood test.
There may be a small cost. There may be a small charge for the test or for drawing the blood. If the test is positive, counseling can be arranged by your doctor. Only about one woman in fifty will need other tests. If you have insurance or Medical Assistance, it may pay for these other tests. If not, the charges may be between $75.00 and $800.00.
A decision has to be made. In those rare cases where a severe detect is found, the parents may want to consider ending the pregnancy. Parents find this to be a very difficult and upsetting decision. If the parents decide to continue the pregnancy, knowing in advance allows the doctors to give the baby the best possible chance. Your doctor and a counselor will be available to help you make the decision.
Should All Pregnant Women Have AFP Screening?
Some couples may need more than routine AFP testing.
Couples who
- have had a previous child with a neural tube defect,
- have a close relative with a neural tube defect, or
- are themselves affected
have a higher risk of having a child with a neural tube defect and should seek genetic counseling and prenatal testing at a Prenatal Diagnostic Center.
However, 95% of all cases of neural tube defects occur in families who have no known personal or family history. For this reason, any pregnant woman may wish to consider AFP screening.
Although the main reason for AFP testing is to screen for neural tube defects, other important information can be learned about the pregnancy. This information will help your doctor to provide you with the best possible prenatal care and improve chances for a healthy baby.
Weigh the pros and cons of AFP screening in light of your individual feelings and circumstances. Discuss the idea, as you would every aspect of your pregnancy, with both your mate and your doctor before deciding.
If An AFP Test is Normal, Can The Mother Be Certain Everything Is All Right With The Baby?
No. Although the AFP test is useful, it does not guarantee a normal baby. It will pick up most, but not all cases of neural tube defects. There are also other kinds of problems which the AFP test cannot detect. But remember, most babies are healthy.
What Will Happen If I Ask For The AFP Screening Test?
You will have a blood test when you are between 16 and 18 weeks pregnant. The blood sample will be sent to the laboratory for analysis. The test will take one to two weeks. Most first tests are normal. However, if your first test is positive, your doctor will be called right away so you can have a second blood test. If this happens to you, do not be upset. REMEMBER, MOST OF THE WOMEN WHOSE FIRST TEST IS POSITIVE STILL HAVE HEALTHY BABIES. If the second test is also positive, your doctor and a counselor will help you decide whether you want to have the additional tests necessary to find out if there is a problem.
Reminders
- Timing is important. Remember to have the first blood sample taken when you are between 16 and 18 weeks pregnant.
- Serum AFP is only the first step. If results are positive, further tests will be needed.
- In the United States, most babies are born healthy - only I or 2 out of 1,000 babies are born with a neural tube defect.
- Maternal serum AFP testing is not perfect. It is only a screening test and can miss a few neural tube defects. However, it offers the best means available for early detection of neural tube defects.
- Occasionally, other birth defects such as an abdominal wall defect, kidney defect, or Down syndrome, may be found.
- If a birth defect is found, additional information and counseling will be available to help you understand the nature of the problem.
- Although the main reason for AFP testing is to screen for neural tube defects, other important information can be learned about the pregnancy. This information will help your doctor to provide you with the best possible prenatal care and improve chances for a healthy baby.
Do You Have Any Questions?
There is a lot to understand about alpha-fetoprotein screening. After reading this information, you may still have questions. Please ask your doctor, or you may call the Maryland Department of Health and Mental Hygiene at (410) 767-6731.
Glossary
Alpha-fetoprotein (AFP): A protein normally produced by the fetus. AFP is present in amniotic fluid and, in smaller amounts, in the mother's blood.
Amniocentesis: A procedure for removing amniotic fluid from the sac surrounding the fetus for testing.
Amniotic Fluid: Water in the sac in the mother's womb in which the fetus develops.
Anencephaly: One type of neural tube defect that occurs when the fetus' head and brain do not develop normally.
Chromosome: Tiny structures in each body cell which contain the genetic information. Normal people have 46 chromosomes in each cell. Extra, missing, broken or abnormal chromosomes cause severe problems in the development of a fetus.
Down Syndrome: A chromosomal abnormality characterized by an extra #21 chromosome. Formerly called mongolism, Down Syndrome causes mental retardation and other medical problems such as heart defects.
Neural Tube Defects (NTD): Birth defects that result from improper development of the brain or spinal cord of a fetus.
Screening Test: A test offered to healthy individuals to identify those who may benefit from additional tests to detect certain conditions.
Spina Bifida: A neural tube defect that results from incomplete closure of the neural tube in the developing fetus.
Ultrasonography (Sonogram): A sound wave picture of the fetus inside the mother's womb.
